Ankopplung eines Ar-Lasers hoeherer Leistung an einen hochflexiblen ummantelten Plastik-Lichtleiter zur Durchfuehrung endoskopischer Photokoagulation - Bodem, F; Reidenbach, H; Fruehmorgen, P; Brand, Hans (Biomedizinische Technik, 1975)
lhft_intern.bib::thirty_years_LHFT_19

An Octave-Bandwidth Double-Balanced Millimeter-Wave Mixer - Schneiderbanger, Dirk; Cichy, A.; Rehner, Robert; Martius, Siegfried; Sterns, Michael; Schmidt, Lorenz-Peter (Proceedings of the 36th European Microwave Conference, 2006)
The paper reports on an octave-bandwidth double-balanced mixer which operates in the millimeter-wave range from 35 to 70 GHz. The design uses a low cost hybrid technology: A thin-film circuit is fabricated on an alumina substrate, and the diodes are flip-chip mounted. Balanced signals are provided by side coupled Marchand baluns. As a result the conversion loss averages out at 13 dB
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.anocta

An Octave Bandwidth Finline Frequency Tripler - Hrobak, Michael; Sterns, M.; Stein, Wadim; Schramm, Marcus; Schmidt, Lorenz-Peter (6th German Microwave Conference, 2011)
In this paper a nearly octave bandwidth frequency tripler based on bilateral finlines is presented. The tripler covers the frequency range from 23 GHz to 40 GHz. The achieved conversion loss averages out at 17 dB. Design and test data of the tripler using antiparallel Schottky diodes are reported. A low cost, easy-to-handle Arlon AD1000 high frequency laminate substrate, processed by rapid prototyping laser decompositioning technique is used. The tripler design flow is based on cooperative-simulation using commercially available 3D fullwave and harmonic balance circuit solvers. A comparison of simulation results and measurement data is given. The impact of the ambiguity at defining the characteristic impedance of the hybrid finline on the simulation results is discussed.
lhft_intern.bib::Hrobak11

An optical directional coupling device with variable coupling - Reidenbach, H; Brand, Hans; Bodem, F; Straetmans, H (Optics and Laser Technology, 1976)
The well known phenomenon of frustrated total internal reflection can be used to design an optical directional coupling device with a continuously variable coupling coefficient. Such a coupler has been designed using two crown glass prisms separated by a narrow gap filled with air or an appropriate liquid. Good agreement of the measured and theoretical coupling coefficients has been observe
lhft_intern.bib::thirty_years_LHFT_33

An Optimization Approach for Robust Transformation of Measured Range Data into Position Estimates in Wireless Networks - Fuentes, Michel Juan Carlos; Vossiek, Martin (IEEE MTT-S International Microwave Workshop on Wireless Sensing, Local Positioning, and RFID, 2009)
This paper introduces a generalized framework for positioning mobile nodes in a wireless network. The transformation of the range data measured between pairs of network nodes into a spatial position is a very challenging task if the range measurements are distorted. Typical distortions in wireless ranging systems are caused by an imperfect clock synchronization or by multipath reflection. The positioning method proposed in this paper overcomes problems of the traditional circular or hyperbolic methods and allows for the detection and elimination of distorted measurements. The positioning is done in a non-Markovian manner, which is an advantage over other available methods, especially the Kalman-based positioning methods, since linear assumptions in the dynamics are avoided. Another advantage of the proposed method is that the two tasks positioning and smoothing are carried out separately. Hence, smoothing of the position data, e.g. by means of a Kalman filter, is possible without the well documented problems in conventional methods induced by the usually applied simplifying assumptions of linear dynamics. The very good performance of the presented approach is demonstrated by real life results obtained in industrial environments. ©2009 IEEE.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.anopti
Keywords: Multipath detection; Parameter Estimation; Positioning; Sequential Monte Carlo Methods

A novel 3-D local position measurement (LPM) technology. Ein neuartiges 3D-Positionsmesssystem - Stelzer, Andreas; Fischer, Alexander; Vossiek, Martin; Söser, T. (11. Internationale Fachmesse mit Kongress für Sensorik & Systemtechnik, Sensor 2003, 2003)
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.anovel

A novel active real-time digital-beamforming imager for personnel screening - Ahmed, S. S.; Schießl, Andreas; Schmidt, Lorenz-Peter (EUSAR 2012, 2012)
Personnel screening is an essential requirement nowadays for securing air traffic as well as critical infrastructures. Several passive and active imaging systems based on millimeter wave technologies were developed to address the demanded security needs. A novel active near-field imager based on two-dimensional sparse array architecture combined with digital-beamforming technique is demonstrated here. The system is fully electronic, and hence operates in real-time to deliver fully focused three-dimensional images of high dynamic range and resolution. A 2 m times 1 m imager is built and demonstrated full agreement with the theoretical design. The imaging concept, measurement technique, and various imaging results are presented.
lhft_intern.bib::Ahmed2012a

A Novel Antenna Placement Algorithm for Compressive Sensing MIMO Radar - Eisele, Bastian; Bereyhi, Ali; Ullmann, Ingrid; Müller, Ralf (2023 IEEE Radar Conference (RadarConf23), 2023)
In colocated compressive sensing MIMO radar, the measurement matrix is specified by antenna placement. To guarantee an acceptable recovery performance, this measurement matrix should satisfy certain properties, e.g., a small coherence. Prior work in the literature often employs randomized placement algorithms which optimize the prior distribution of antenna locations. The performance of these algorithms is suboptimal, as they can be easily enhanced via expurgation. In this paper, we suggest an iterative antenna placement algorithm which determines the antenna locations deterministically. The proposed algorithm locates jointly the antenna elements on the transmit and receive arrays, such that the coherence of the resulting measurement matrix is minimized. Numerical simulations demonstrate that the proposed algorithm outperforms significantly the benchmark, even after expurgatio
Keywords: Compressive sensing; MIMO radar; Antenna placement; coherence

A Novel Approach for Modeling and Digital Generation of RF Signals Distorted by Bandlimited Phase Noise - Tschapek, Peter; Körner, Georg; Fenske, Patrick; Carlowitz, Christian; Vossiek, Martin (IEEE Journal of Microwaves, 2022)
In radar and communication systems, phase noise is one of the main causes of performance degradation. Phase noise increases the uncertainty in radar measurements and limits the achievable data rates in communication systems. When radio frequency (RF) signals distorted by bandlimited phase noise are modeled, the phase noise power spectral density (PSD) is usually approximated by a scalar root-mean-square (RMS) phase error derived from a simple integration of the PSD. This disregards the close-to-carrier noise excess. In this article, we show that this convention simplification describes the real behavior of phase noise inadequately. In addition, we present a simulation of realistic phase noise behavior. The novel additive colored noise (ACN) model requires a representative phase noise PSD of the phase-locked loop (PLL) signal generator phase noise to be modeled. The developed ACN approach is validated by comparing the measured PSD of different PLL signal generators with the respective simulated RF signals distorted by phase noise. As a simple metric for assessing the quality of the phase noise models, we use the influence of phase noise on carrier frequency estimation. It is shown that the novel approach shows a significant improvement in the agreement between the simulated and measured precision compared to standard additive white Gaussian noise (AWGN) models. The results show that advanced phase noise models, as proposed in this paper, are necessary to adequately model and predict the performance of radar and communication system
Keywords: Phase noise; RF signals; Stochastic processes; Noise measurement; Frequency estimation; Phase measurement; Frequency shift keying

A Novel Approach in Raman Temperature Sensing in Optical Fiber based on Broadband Incident Light - Renner, Esther; Härteis, Lisa-Sophie; Weiss, Nico; Schmauß, Bernhard (OSA Technical Digest, 2021)
We describe a new approach in Raman temperature sensing based on broadband incident light. The reported results show the proof of concept and thus form an important basis for future distributed temperature sensing systems.

A Novel Approach to Entirely Integrate Virtual Test into Test Development Flow - Lu, Ping; Glaser, Daniel; Uygur, Gürkan; Helmreich, Klaus (Proceedings, 2009)
In this paper, we present an open architecture Virtual Test Environment (VTE) which can be easily integrated into various modularized Automatic Test Systems (ATS) compliant to Open Standard Architecture (OSA). The focus of this paper is to analyze and address the major issues that still prevent the application of Virtual Test (VT) from day-to-day's practice. As a pilot demonstration, a VHDLAMS based VTE is established and an ADC test is performed. The environment is intended to seamlessly interoperate with the test system during test program development procedure. © 2009 EDAA.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.c3scha.anovel
Keywords: ATML; Hardware description language; IEEE1641; Simulation; Test generation; VHDL; Virtual Test

A Novel Concept for Dynamic Network Reduction Dedicated to Real-Time Application - Kuri, Ananya; Gäbel, Sebastian; Burlakin, Ilya; Wagner, Timo; Mehlmann, Gert; Luther, Matthias (Kyoto Symposium 2022 - CIGRE Japan, 2022)
An increasing power electronic based generation and distribution causes new requirements for the power system. It pushes the limits of hardware and software resources for modelling and simulation while demanding more accuracy, with modern methods for analysis [1]. Therefore, stakeholders increasingly insist on analyzing the new source’s interactions and impacts on the power grid under offline and real-time environments. In power system engineering, real-time simulators form the interface between the virtual and real-world and assess electrical equipment and control. Thus, they serve as a tool for digital twins. The simulation of dynamic phenomena requires a plausible network model with the device under test to assess those interactions accurately. This is achieved by a suitable dynamic reduction of the grid areas to be investigated, with complex reduction process requirements. Historically the main reason for dynamic network equivalents was the limited CPU capacity enabling steady-state and dynamic calculations on extended networks. The results often had a reasonable degree of approximation. Modern computers are equipped with performant multi-core CPUs and large RAM, yet dynamic network equivalents of extended grids are still used nowadays. One of the main reasons for developing model equivalents is to accurately reproduce and simulate complex inverter-based equipment and depict its interaction with the network in software tools and real-time simulators. Due to the control structure, among other things, integration time steps are often chosen in the microsecond range. Hence, such simulations usually take ample time and require high processing power. This is a usual concern when equipment test matrices with several hundred cases have to be dealt with. Simulating a network and the device under test in a real-time environment has additional challenges. Several approaches and tools to achieve reduced networks are available; however, none of the approaches are customized to achieve reduced models for real-time simulators. The paper highlights a dynamic model reduction methodology that accommodates real-time requirements. The methodology concentrates on achieving a high degree of reduced grid elements focusing on the real-time simulator requirements and developing an interactive user automation process. The dynamic reduction process is based on a hybrid methodology of machine coherency and estimation-based equivalent methods achieved via Multi-Objective Genetic Algorithm NSGA-II presented in [2]. The paper focuses on the next phase of transferring the equivalent developed in an offline environment to the real-time environment considering the hardware requirements and automating the process. The reduced model of the targeted network area consists of a physically realistic grid model rather than a mere mathematical equivalent and is therefore suited for real-time simulations with hardware-in-the-loop (HIL). The complete path and endeavor from developing offline equivalents to emulating the complete system on real-time hardware is the prime focus of the paper.<br

A Novel Concept for Vehicle 2D Pose Estimation Using Automotive SIMO FMCW Radar Sensors in a Bistatic Vehicle-to-Infrastructure Network - Fenske, Patrick; Brückner, Stefan; Kögel, Tobias; Vossiek, Martin (2024 IEEE Radar Conference (RadarConf24), 2024)
This paper presents an approach for the use of cooperative FMCW radar units for precise vehicle-to-infrastructure localization, orientation determination, and simultaneous estimation of synchronization errors between the involved wireless nodes. Our concept requires only one stationary SIMO radar node, which is integrated into the infrastructure and a conventional automotive radar mounted on the vehicle. To enable real-time operation, an extended Kalman filter tracks the relative position and orientation, as well as the time and frequency offsets of the two radar units. The proposed algorithm is evaluated through various measurements. The results show a precise localization capability, with a 2D position RMSE of less than 1 cm. The achieved synchronization accuracy is in the time range of 100 ps, with femtosecond precision.<br
Keywords: Location awareness; Vehicle-to-infrastructure; Radar detection; Radar; Radar tracking; Real-time systems; Sensors

A Novel DGS-Marchand balun from 40 to 80 GHz with IF-tap for mixer design - Rehner, Robert; Schneiderbanger, Dirk; Sterns, Michael; Martius, Siegfried; Schmidt, Lorenz-Peter (IEEE MTT-S International Microwave Symposium July, 2007)
UnivIS-Import:2015-04-16:Pub.2007.tech.IE.LEH.anovel

A Novel, Efficient Algorithm for Subsurface Radar Imaging below a Non-Planar Surface - Ullmann, Ingrid; Vossiek, Martin (Sensors, 2023)
In classical radar imaging, such as in Earth remote sensing, electromagnetic waves are usually assumed to propagate in free space. However, in numerous applications, such as ground penetrating radar or non-destructive testing, this assumption no longer holds. When there is a multi-material background, the subsurface image reconstruction becomes considerably more complex. Imaging can be performed in the spatial domain or, equivalently, in the wavenumber domain (k-space). In subsurface imaging, to date, objects with a non-planar surface are commonly reconstructed in the spatial domain, by the Backprojection algorithm combined with ray tracing, which is computationally demanding. On the other hand, objects with a planar surface can be reconstructed more efficiently in k-space. However, many non-planar surfaces are partly planar. Therefore, in this paper, a novel concept is introduced that makes use of the efficient k-space-based reconstruction algorithms for partly planar scenarios, too. The proposed algorithm forms an image from superposing sub-images where as many image parts as possible are reconstructed in the wavenumber domain, and only as many as necessary are reconstructed in the spatial domain. For this, a segmentation scheme is developed to determine which parts of the image volume can be reconstructed in the wavenumber domain. The novel concept is verified by measurements, both from monostatic synthetic aperture radar data and multiple-input–multiple-output radar data. It is shown that the computational efficiency for imaging irregularly shaped geometries can be significantly augmented when applying the proposed concep
Keywords: radar; subsurface imaging; synthetic aperture radar; ground penetrating radar; MIMO radar; non-destructive testing

A Novel Fabrication Process for Printed Antennas Integrated in Polymer Multi-Layer Car Body Panels - Kilian, Andreas; Schmidt, Lorenz-Peter (Proceedings of the 39th European Microwave Conference, 2009)
The complete fabrication process for the construction of printed millimeter-wave antennas integrated in plastic multi-layer car body panels is presented. Starting from material characteristics and fixed parameters obtained by the investigation of single process steps, the design of microstrip patch antennas at 24GHz will be demonstrated. The fabrication is based on the hot embossing technology for the metallization of a polymer film used as antenna substrate. The antenna feed is realized by laser processing the ground plane, drilling the substrate and via connecting to the back side. The antenna is embedded within the plastic multi-layer structure by laminating a paint foil and reinforcing the part by back injection molding. The comparison between simulation and measurement results gives information about the realizability of plastic integrated millimeter-wave antennas and criteria for future design revisions. Far-reaching potentials of this process are associated with the construction of conformal integrated antenna arrays for automotive radar applications. © 2009 EuMA.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.anovel

A Novel Fully Electronic Active Real-Time Imager Based on a Planar Multistatic Sparse Array - Ahmed, Sherif Sayed; Schiessl, Andreas; Schmidt, Lorenz-Peter (IEEE Transactions on Microwave Theory and Techniques, 2011)
lhft_intern.bib::ahmed2011

A Novel Interlaced Chirp Sequence Radar Concept with Range-Doppler Processing for Automotive Applications - Thurn, Karsten; Shmakov, Denys; Li, Gang; Max, Stephan; Meinecke, Marc Michael; Vossiek, Martin (2015)
In this paper, we introduce a novel concept for primary frequency-modulated continuous-wave (FMCW) radar. The approach is based on a phase locked loop-controlled interlaced chirp sequence (ICS) waveform and, in contrast to basic range-Doppler processing, it enables higher target velocities to be detected. It is thus very suitable for automotive applications. The interlaced ramps in the system are generated by two separate frequency synthesizers. These are combined by an RF switch to suppress transients caused by oscillator overshoot and to avoid incoherencies due to programming times of the phase locked loop (PLL) ICs. A prototype radar system was realized in K-Band. Promising test results bode well for other application

A Novell Wireless Forklift Positioning System for Indoor and Outdoor Use - Fuentes, Michel Juan Carlos; Millner, Hendrik; Vossiek, Martin (5th WORKSHOP ON POSITIONING, NAVIGATION AND COMMUNICATION 2008 (WPNC?08), 2008)
Precise tracking of industrial transportation means - e.g. automatic guided vehicles, cranes, forklifts, etc. - is becoming increasingly important for optimizing logistics processes and storage management. Real time forklift tracking can supplement or replace RFID systems in applications where flexible storage is wanted, where real time information is needed or when item tagging is inappropriate due to costs or physical constrains. In this paper a high performance 5.8 GHz wireless forklift positioning system is introduced. Round-trip time-of-flight (RTOF) measurements provide a set of ID distance values between an arbitrary number of mobile and fixed secondary radar units attached to the forklift and to the infrastructure, respectively. With an optimized geometry based heuristic localization method the position and orientation of the forklift is derived. The proposed method can deal with faulty RTOF measurements, e.g. due to multipath distortions, and it enables a robust and reliable localization. The proposed RTOF system concept allows a minimal complexity of the infrastructure since no backbone network and no dedicated synchronization scheme is needed. An indoor test campaign with a forklift in a steel mill proved a measurement uncertainty of position and orientation below ±5 cm and ±10°, respectively, even without the use of any assisting inertial or dead reckoning sensors. This outstanding performance makes the system ideally suited for various applications in production, logistics and storage. ©2008 IEEE.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.anovel
Keywords: Extended kalman filter; Location and tracking; Parameter estimation; Radio navigation; Vehicle tracking

A Novel Manufacturing Method for Microwave Components by Lost Wax Casting - Panusch, David; Pelchen, Lucas; Müller, Sebastian; Gold, Gerald (IEEE Access, 2023)
A novel manufacturing strategy for the detailed fabrication of complex and mechanically robust microwave components is presented. Additive printing of the full wax positive model with a multijet printer allows free shaping on the one hand, while metal casting provides mechanical stability for a variety of applications on the other. In addition to that a slotted waveguide model is used to improve the post-processing and performance. This combination is used with a rectangular waveguide for the E-band to demonstrate the performance of this manufacturing method at higher frequencies than previous publications. Measurements on the samples show comparable attenuation coefficients to the milled split-block counterpart, i.e., less than 5 dB/m, a good root mean square (RMS) surface roughness of the inner surfaces with S q = 5.85 μm and astonishingly fine tolerances of 8.8±40.3 μm overall. Comparisons are also made between other published additive manufacturing processes.<br
Keywords: Optical waveguides Casting Attenuation Metals Surface waves Microwave theory and techniques Surface treatment Three-dimensional printing

A Novel Method for UHF RFID Tag Tracking Based on Acceleration Data - Parr, Andreas; Miesen, Robert; Kirsch, Fabian; Vossiek, Martin (6th Annual IEEE International Conference on RFID (IEEE RFID 2012), 2012)
Options for RFID tag tracking and localization are an essential asset for future high performance RFID reader systems. A reader with long reading range, high reading rate and multi-tag capability should be able to assist the user to find / retrieve tags, to create spatial object maps and to restrict the reading range to specific regions of interest. In this paper we introduce a novel method for RFID tag tracking with a moving for example handheld reader. An inertial measurement unit (IMU) is used to characterize the handheld trajectory. Contrary to approaches where IMU locations are reconstructed via double integration of the acceleration data, our novel technique only uses acceleration data without knowledge of the actual antenna locations. Inexpensive, standard inertial sensors can be used in this approach, and the usual drift and offset issues associated with IMU-based positioning are avoided. Parallel to the IMU acceleration data, the phase of the backscattered RFID signal is input. Double differentiation of the signal phase yields a second acceleration data set. By comparing the IMU and the RFID signal phase acceleration data, the direction of arrival of the RFID signal is estimated using a quasi-spatial optimal filter. This paper introduces the novel RFID tracking approach and illustrates its capability with numerical simulations and experimental results. This novel approach is a simple, yet promising, solution which can be implemented in any handheld reader and will improve its functionality considerably. © 2012 IEE
UnivIS-Import:2015-04-16:Pub.2012.tech.IE.LEH.anovel_8
Keywords: angle of arrival; phase measurement; UHF RFID

A Novel Micron-Thick Whisker Contacted Schottky Diode Chip - Grueb, A; Simon, A; Hartnagel, H; Brune, J; Raum, M; Brand, Hans (1995)
lhft_intern.bib::thirty_years_LHFT_381

A Novel Sequential Monte Carlo Method Based Synthetic Aperture Reconstruction Approach for Real-Time 3D Wireless Local Positioning - Li, Gang; Ebelt, Randolf; Vossiek, Martin (Frequenz, 2012)
In this paper, we introduce a precise real-time 3D indoor localization concept using a combination of the MISAS (multilateral inverse synthetic aperture secondary radar) approach and SMCM (sequential Monte Carlo method). The synthetic aperture approach is a promising locating technique with effective multipath suppression. However, its practical use is restricted by the huge computational load of the reconstruction algorithms. We use a weighted-particle set-which we reduce subsequently by resampling-to represent the PDF (probability density function) instead of the highly complex, standard, grid-based approach. Simulation runs and experiments, carried out with a 5.8 GHz FMCW secondary radar system with a bandwidth of only 140 MHz, show that a robot TCP (tool center point) can be localized in 3D in the mmrange using a few hundred particles and operating in a dense multipath environment. This novel extension is a promising solution for real-time, 3D MISAS localization applications.
UnivIS-Import:2015-03-09:Pub.2012.tech.IE.LEH.anovel_9
Keywords: FMCW secondary radar; Indoor wireless positioning; Sequential Monte Carlo method; Synthetic aperture radar

A Novel System for Systematic Microwave Noise and DC Characterization of Terahertz Schottky Diodes - Biber, Stephan; Cojocari, O.; Rehm, Guenther; Mottet, B.; Rodriguez-Girones, M.; Schmidt, Lorenz-Peter; Hartnagel, H. (IEEE Transactions on Instrumentation and Measurement, 2004)
An automated system is developed to evaluate a large number Schottky diodes for terahertz applications with respect to their dc and noise characteristics using a highly sensitive noise measurement technique for one port devices. An extensive RF switching matrix allows noise characterization of one port devices at selected frequency points over a bandwidth from 2 to 8 GHz. The measurement principle also accounts for the impedance mismatch between the system and the device under test (DUT). Furthermore, the setup includes an automated three-axis nanopositioning system capable of consecutively contacting many Schottky diodes arranged in a honeycomb array. The highly accurate positioning of the DUT allows to create reproducible contacts with the diodes using electrochemically etched whisker tips. The smooth contacting procedure enables several hundred contacts with the same whisker tip. With this system, we evaluate the statistical distribution of dc and noise parameters of Schottky diodes with an anode diameter of 1 μm within one honeycomb chip. The system helps in optimizing the production parameters of Schottky diodes for terahertz frequencies.
UnivIS-Import:2015-03-09:Pub.2004.tech.IE.LEH.anovel
Keywords: Noise; Schottky diodes; Terahertz (THz)

A Novel Ultra-Broadband and Low-Cost Termination Concept Based on a Dual-Layer SIW Topology - Birkenhauer, Christoph; Vossiek, Martin (2021 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS), 2021)
In this work a novel concept to realize wideband matches at high frequencies with standard manufacturing processes without the need for additional fabrication steps or materials is presented. This is achieved by incorporating the high dielectric losses in substrates based on epoxy and glass fibers. The benefits of this approach for real applications are demonstrated by the design and fabrication of an illustrative load. This wideband match was then validated with an absolute reflection coefficient of around −20dB between 50 and 110GHz. Parameters critical for performance are presented and their impact is examined in theory and verified by full wave simulations and measurement
Keywords: substrate integrated waveguide; SIW; match; load; termination; V-band; E-band; W-band; millimeter-wave; mmW

A Novel Ultra-Broadband Low-Loss Bond-Wire Interconnect Design Concept Applied to a 2 GHz to 135 GHz Substrate-to-Substrate Interface - Pfahler, Tim; Scheder, André; Bridier, Anna; Schür, Jan; Vossiek, Martin (2023 IEEE/MTT-S International Microwave Symposium - IMS 2023, 2023)
This work presents a design concept for ultra-broadband bond-wire interconnects between two alumina substrates from 2 GHz up to 135 GHz. Due to the rethinking of the substrate assembly and optimization of the CPW bond-wire transmission line interface, the currently existing limitations in terms of a narrowband matching bandwidth and high insertion loss of state-of-the-art interconnects can be eliminated. The resulting key advantage of the proposed design is the ultra-broadband characteristic that exhibits lowest impedance discontinuity and thus realizing an excellent matching bandwidth of more than 130 GHz. The measured return loss is higher than 25 dB with an insertion loss of less than 1.6 dB over the entire frequency band. The paper highlights both, the electric considerations as signal routing and the assembly part for achieving a robust, reproducible and fully mmW-transparent interconnect even beyond 100 GHz. Due to the broadband performance and the high agreement of simulation and measurement results the proposed interconnect and the underlying design and assembly considerations set a new benchmark for interconnect design. Moreover, this approach can be used for signal transitions in applications such as broadband communication systems, high-resolution radar sensing and measurement and test applications.<br

A novel UWB chirp sequence radar signal processing concept for chipless RFID based vehicle localization - Pöpperl, Maximilian; Gottinger, Michael; Hoffmann, Marcel; Jakoby, Rolf; Vossiek, Martin (2017 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM), 2017)
Localization of vehicles in industrial environments is a challenging task due to the high demands on the radar system because of harsh environmental conditions and strong multipath propagation. Chipless radio identification (RFID) is well suited for this type of task due to its low-cost production and extreme robustness against environmental influences. Furthermore, RFID transponders based on time domain reflectometry can be interrogated by chirp sequence radar systems. To achieve high data capacities and acceptable tag dimensions, we use an ultra-wideband system. High integration/measurement times that are reasonable yield increased velocity resolution and sufficient signal-to-noise ratios. If a 2D-FFT-based processing step is applied, the high measurement time combined with the high relative bandwidth lead to a smearing in velocity and range dimensions, which significantly diminishes system performance. We first investigate the reasons for this effect, which prevents the TDR RFID transponder from being decoded, and then propose appropriate remedial action. We verify the applicability of the presented UWB chirp sequence processing technique to localize vehicles using chipless RFID by experiments in a laborator

An overview of RFID localization techniques - Vossiek, Martin; Miesen, Robert (IEEE Topical Conference on Wireless Sensors and Sensor Networks (WiSNet), 2012)
lhft_intern.bib::Vossiek2012a

Antenna Array Calibration Using a Sparse Scene - Geiß, Johanna; Sippel, Erik; Hehn, Markus; Vossiek, Martin (IEEE Open Journal of Antennas and Propagation, 2021)
In radar systems, antenna arrays acquire direction-dependent information to localize targetsor create images of the environment. However, because of unknown complex amplitudes per channel andmutual coupling, a calibration is necessary for good performance. Common calibration approaches measureto targets under known angles in a multipath-free far-field environment, which often can only be providedby anechoic chambers. Therefore, this process is not suitable for low-cost and frequent calibration. Toovercome these limitations, this paper proposes a novel calibration approach using an unknown but sparsetarget scene. Multiple measurements at known relative positions of the radar are combined to a syntheticaperture. Then, the full mutual coupling matrix is estimated simultaneously with the unknown target scene.The method requires neither target position information, far-field conditions, nor an anechoic chamberbecause multipath propagation can be suppressed easily for targets located in the near-field. The proposedcalibration approach is validated by measurements of a commercial 77 GHz radar. The performance isevaluated by comparing the achieved image quality using the calibration results of this work and theradar’s ex-factory calibration data. The proposed novel calibration procedure improves the image quality,while considerably lowering the demands on the calibration measurements and environmen

Antenna Concept for an Automotive Radar Sensor at 150 GHz - Köhler, Mike; Schür, Jan; Schmidt, Lorenz-Peter (IEEE Radio Wireless Week 2013, 20-23 Jan., 2013)
Current Automotive Radar sensors operate in a frequency range up to 81 GHz to provide distance, velocity and angle information about traffic objects. For detecting weakly reflecting objects in presence of a nearby strong reflector (e.g. a person standing close to a van) there are high demands on a radar systems angular resolution. A possibility to improve the angular resolution is increasing the operation frequency. In this paper an antenna concept at 150 GHz is presented showing the benefits of high resolution radar for cars. © 2013 IEEE.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.antenn

An Ultra-Efficient Approach for High-Resolution MIMO Radar Imaging of Human Hand Poses - Bräunig, Johanna; Wirth, Vanessa; Kammel, Christoph; Schüßler, Christian; Ullmann, Ingrid; Stamminger, Marc; Vossiek, Martin (IEEE Transactions on Radar Systems, 2023)
The capturing of hands, including their poses, shapes and motions, has numerous potential applications, such as human-machine interfaces and medical use cases. However, in the radar context, most existing methods only allow for the recognition of dynamic hand gestures based on Doppler evaluations due to the respective systems’ limited lateral resolution. Radar-based high-resolution three-dimensional (3D) imaging using multiple-input multiple-output (MIMO) radars is currently the state-of-the-art in personnel security scanning. However, the associated imaging techniques suffer from computationally burdensome reconstruction algorithms that sample the entire 3D space of interest, thereby making them less suitable for real-time applications. Moreover, their application in hand motion tracking scenarios is limited by low frame rates that result from a high number of transmit frequencies. Hence, we present an efficient and powerful approach for the radar-based 3D reconstruction of hand poses. The method extends the frequency shift keying continuous wave radar principle and reconstructs the hand surface using only two carrier frequencies. Instead of reconstructing an entire 3D volume, only two single-tone radar images are computed. Depth information is derived from phase differences between corresponding pixels in the images. The approach significantly reduces computational load by three orders of magnitude compared with the state-of-the-art and enables higher frame rates. Within this paper, this novel reconstruction principle is analyzed and compared to a state-of-the-art radar imaging approach using a MIMO radar system with 94 transmitting and 94 receiving antennas. Detailed simulations of point targets and comprehensive measurements demonstrate the excellent imaging performance of our approac

An Ultrasonic Multielement Sensor System for Position Invariant Object Identification - Vossiek, Martin; Magori, V.; Ermert, Helmut (IEEE International Ultrasonics Symposium, 1994)
This paper describes an ultrasonic sensor system for application in air that is capable of recognizing workpieces with size up to 20 mm, independently of their position and orientation, with high reliability. The 4x4 Transducer Matrix signals are first processed with a simplified reconstruction algorithm that leads to position invariant axial profiles of the object reflectivity. A broadband holographic reconstruction is then performed for those object planes that are reflecting the main signal energy. The Zernike Moments of the resulting cross-sectional patterns and features of the reflectivity profiles are fed in a 3-layered perceptron network. The system has been tested with a set of measuring data from 25 typical workpieces. Even though some objects have very similar reflection properties, it is possible to identify the objects in an area of 25x25 mm2 independently of their position and orientation with a recognition rate higher than 99%.
UnivIS-Import:2017-12-18:Pub.1994.tech.IE.LEH.anultr

An ultrasonic sensor network for high-quality range-bearing-based indoor positioning - Flores, Sergio Alberto; Geiß, Johanna; Vossiek, Martin (IEEE/ION Position, Location and Navigation Symposium, PLANS 2016, 2016)
We present an indoor positioning system based on time-of-arrival (TOA) and angle-of-arrival (AOA/bearing) estimations using ultrasonic signals. Sensor anchor nodes deployed in the area of interest detect incoming signals from a mobile ultrasonic transmitter. The developed algorithm uses the range-bearing positioning method and can deal with ambiguous AOA sensor data. The system delivers 2D locations. We tested our positioning system inside an office building. Our system can locate objects with an error well below 10 cm even under these conditions with multipath reflection
Keywords: angle-of-arrival; local positioning system; range-bearing positioning; ultrasonic sensors

An ultrasonic sensor system for location gauging and recognition of small workpieces. Ein Ultraschall-Sensorsystem zur Erfassung und Erkennung kleiner Werkstücke. - Vossiek, Martin; Magori, V.; Ermert, Helmut (7. Internationale Fachmesse mit Kongreß für Sensoren, Meßaufnehmer & Systeme, Sensor 95, 1995)
UnivIS-Import:2017-12-18:Pub.1995.tech.IE.LEH.anultr

An Ultra-Versatile Massive MIMO Transceiver Testbed for Multi-Gb/s Communication - Gröschel, Patrick; Hehn, Markus; Sippel, Erik; Schober, Robert; Weigel, Robert; Vossiek, Martin; Carlowitz, Christian (2019 IEEE 2nd 5G World Forum (5GWF), 2019)
Massive multiple-input multiple-output (MIMO) communication has gained huge attention throughout the last years as a key technology for fifth generation mobile communication systems, because they enable wide area coverage along with ultra-high data rates and low bit energy. Furthermore, for a high number of antennas, communication theory predicts nearly optimal performance using basic linear detection and precoding schemes. However, realizing such large-scale arrays (say 100 elements or more) is non-trivial and costly and hence, only few of them are available for public research. Most often, existing solutions are limited to the current mobile communication standards. We therefore propose the design and implementation of a low-cost ultra-versatile 120-antenna massive MIMO testbed applicable both in communication and localization research. An instantaneous bandwidth of 150 MHz at a center frequency of 5.8 GHz is covered. An indoor verification measurement with 24 parallel transmissions and a bandwidth of 125 MHz achieved a sum-rate of 22.8 Gb/s with only 1.02 % bit error rate resulting in an outstanding equivalent error-free spectral efficiency of 167.2 bit/s/Hz.<br
Keywords: Radio frequency; Antenna arrays; Antenna measurements; OFDM; Transceivers

An Ultra-Wideband DC-Block on Thin-Film Ceramic for the Next Generation of Test and Measurement Applications Up to 150 GHz - Scheder, André; Pfahler, Tim; Bridier, Anna; Schür, Jan; Vossiek, Martin (2023 53rd European Microwave Conference, EuMC 2023, 2023)
This paper presents an ultra-wideband DC-Block directly integrated into a 50 ohm microstrip line manufactured on a 4 mil thick alumina substrate. The DC-Block features a low frequency 3 dB cutoff at 37 MHz and a measured resonance-free operation up to 150 GHz. Its excellent return loss of at least 20 dB and low insertion loss of less than 1.1 dB makes it a perfect choice for the next generation of test and measurement applications from nearly DC up to 150 GHz.
CRIS-Team Scopus Importer:2023-12-01
Keywords: bias-tee; ceramics; dc-block; measurement and test; mmW; ultra-wideband

An Ultra-Wideband Local Positioning System for Highly Complex Indoor Environments - Waldmann, Benjamin; Ebelt, Randolf; Vossiek, Martin; Weigel, Robert (International Conference on Localization and GNSS (ICL-GNSS) 2012, 2012)
In this paper a novel approach for a high precision local positioning radar using an ultra-wideband (UWB) technique is presented. The concept is based on the standard frequency modulated continuous wave (FMCW) radar principle combined with short pulses to fulfill the emission limits given by the official regulatory authorities. Besides the well known advantages of a FMCW radar, the proposed system implies a wide frequency bandwidth. With this concept, a high accuracy in dense multipath indoor environments can be achieved, ideally suited for 1D, 2D, and 3D localization applications for complex industrial environments. Investigations on the achievable performance of such an UWB system show very promising results and are presented within this paper. A prototype system was fabricated which operates at the center frequency of 7.5 GHz utilizing a bandwidth of 1 GHz. With the setup presented in this paper the distance between two wireless units can be measured achieving a standard deviation and absolute accuracy in the low centimeter range, even in challenging multipath environments. © 2012 IEEE.
UnivIS-Import:2015-04-16:Pub.2012.tech.IE.LEH.anultr

An Ultra-Wideband Microstrip Gain Equalizer on Thin-Film Ceramic for Future Millimeter Wave Applications up to and Beyond 120 GHz - Scheder, André; Pfahler, Tim; Bridier, Anna; Vossiek, Martin (2024 IEEE Wireless and Microwave Technology Conference (WAMICON), 2024)
This paper presents the design, simulation and characterization of an ultra-wideband microstrip gain equalizer (EQ) on thin film ceramics. The work thoroughly elaborates the design process of how to design a millimeter wave EQ, transforming a standard RF attenuator into an RF compatible gain equalizer. To reach best performance, state of the art microwave manufacturing techniques and materials like alumina, sputtered thin film resistors and laser trimming were used. The proposed design enables a simple, gain equalization slope adjustment only by setting two resistance values accordingly. It can also be adapted to other substrate materials and thicknesses as well as lower and higher frequency ranges. To verify the performance achieved in simulation, multiple samples were fabricated and measured. The measured samples exhibit ultra low measurement variance, indicating a tolerance-insensitive design and excellent manufacturing of the specimen. The manufactured EQ features a broadband operating frequency range from 60 GHz to 120 GHz, resulting in a relative bandwidth of 67%. Its excellent measured return loss of at least 15 dB and low insertion loss of 1 dB make it an excellent choice for future millimeter wave applications of up to 120 GHz and beyond.<br
Keywords: Radio frequency; Equalizers; Millimeter wave technology; Millimeter wave measurements; Loss measurement; Ceramics; Electrical resistance measurement; Ceramics; gain equalizer; ultra-wideband; millimeter wave; thin film technology

An Ultra-Wideband Time Domain Reflectometry Chipless RFID System with Higher Order Modulation Schemes - Pöpperl, Maximilian; Carlowitz, Christian; Vossiek, Martin; Mandel, Christian; Jakoby, Rolf (Proceedings of the 10th German Microwave Conference (GeMiC 2016), 2016)
lhft_intern.bib::Poepperl2016a

An X-band phased array microwave/photonic beamforming network - Kirsch, Fabian; Banerjee, S.; Zimmer, G.; Feldle, H.; Marten, P.; Schmidt, Lorenz-Peter (1993)

A particle swarm optimizer for tuning a software-defined, highly configurable wireless power transfer platform - Schütz, Martin; Georgiadis, Apostolos; Collado, Ana; Fischer, Georg (Wireless Power Transfer Conference (WPTC), 2015 IEEE, 2015)

A physical model for skin effect in rough surfaces - Gold, Gerald; Helmreich, Klaus (42th European Microwave Week, 2012)
Insertion loss measured on PCB transmission lines operated in the two-digit Gigahertz range yields responses that exceed those simulated with geometry and material parameters. At such frequencies, the loss due to skin effect can no more be calculated assuming perfectly smooth conductor surfaces, as the skin depth would reach and fall below the dimension of surface roughness. Various phenomenological and topological models have been presented to account for this issue. Phenomenological models tend to need additional parameters to correct for new materials and frequency ranges, while topological models inherently use many parameters and often require significant computation effort. As an alternative, this paper suggests a comprehensive, single-parameter and fast computable physical model that accurately predicts measured response
lhft_intern.bib::Gold2012

A Physical Surface Roughness Model and Its Applications - Gold, Gerald; Helmreich, Klaus (IEEE Transactions on Microwave Theory and Techniques, 2017)
This paper covers the essential aspects of modeling surface roughness for microwave applications based on underlying physics. After a short summary of the relevant field theoretical fundamentals, surface roughness metrology and commonly used roughness parameters are described. Existing models and their limitations are discussed before the recently proposed Gradient Model is introduced. To this purpose, the modeling approach, the derivation from Maxwell's equations, model predictions, and their experimental verification are shown. Reasonable choices for effective material parameters reflecting the electromagnetic effects of surface roughness as well as a corresponding surface impedance concept are derived. Both concepts allow for easy application of the Gradient Model with 3-D field solvers or analytical models. The obtained simulation results illustrate roughness impact on loss and phase delay in typical transmission lines. Comparison to measurement results up to 100 GHz shows that the Gradient Model accurately predicts these quantities for rough conductor surfaces. As it is not limited to transmission lines only, it significantly improves the design process for arbitrary microwave applications with 3-D field solvers for this frequency range.

A power-stable CO2 laser with ceramic resonator frame - Bartosch, Thorsten; März, Martin (Review of Scientific Instruments, 1995)
A CO2 laser with a resonator frame made of low expansion ceramics has been developed to provide superior passive stability properties. High stiffness, low specific weight, and very good electric insulation properties recommend ceramic as an attractive material for many laser applications. The long-term power stability of a first prototype was better than ±0.44% measured over 15 min, the short-term stability was better than ±0.24%. Both values were achieved without any active stabilization technique, without damping of external vibrations, and with a non-temperature-controlled coolant. With a new switch mode power supply without ballast resistor a wall-plug efficiency of about 14% has been achieved under quasi-sealed-off conditions. The specific laser output power was about 20 W/m at a gas pressure of 18.5 mbar and a gas mixture He:N2:CO 2=75:15:10+5.5% Xe. © 1995 American Institute of Physics.
Created from Fastlane, Scopus look-up

Applicability and Performance of Standard Compression Methods for Efficient Data Transmission and Storage in Radar Networks - Körner, Georg; Hoffmann, Marcel; Stief, Patrick; Zhang, Mengyu; Rückert, Rainer; Herglotz, Christian; Kaup, André; Vossiek, Martin (IEEE Journal of Microwaves, 2021)
Modern sensor networks—those used for autonomous driving, security systems, human motion tracking, or smart city/smart factory applications—are shifting to a more centralized data processing approach to enable efficient multimodal sensor fusion for optimal environment perception in complex dynamic situations. Among lidars and cameras, radars are typical for these applications, but they generate huge amounts of data, which cannot be transmitted or stored effectively in current setups. Consequently, manufacturers usually have to process the data “on sensor.” This results in transmitting only a few extracted features as point clouds or object lists to a central processing unit, which usually causes a significant loss of information. With this approach, advanced processing—such as enhancement of resolution by coherent combination of sensors or ghost target removal with advanced algorithms—is hardly possible. To overcome this, we suggest an alternative method by using signal-based compression with defined losses. The following topology will be proposed: the sensors encode raw data without prior radar-specific processing and after transmission, a central unit decodes and processes the radar data, thus benefiting from its more powerful heterogeneous processing system. We will analyze lossless compression algorithms with rate savings of about 30% to 65%, but the focus is on lossy compression algorithms that incorporate higher compression ratios by allowing negligible errors. It is shown that state-of-the-art multimedia compression algorithms can obtain rate savings of 99%, and radar specific algorithms can add a 50-fold gain on top, reaching 99.98%. To assess the distortions of compressed data, we then present different radar-specific evaluation metrics.
Keywords: Radar; OFDM modulation; OFDM; Radar antennas; Compression algorithms; data compression; source coding; FMCW radar; Radar applications; Process control; Antennas

Applicability of the AM-PM Conversion Method to Beam Position Monitoring of Electron Beams accelerated in S-Band Frequency Range - Ruf, M.; Quednau, Philipp; Schmidt, Lorenz-Peter; Setzer, S. (10th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators, DIPAC2011, 2011)
lhft_intern.bib::Ruf11

Application of a digital non-linear compensation algorithm for evaluating the performance of root-raised-cosine pulses in 112 Gbits-1 DP-QPSK transmission - Asif, Rameez; Usman, Muhammad; Lin, Chien-Yu; Schmauß, Bernhard (Journal of Optics, 2012)
In this paper, we numerically investigate the non-linear tolerance of root-raised-cosine (RRC) pulse shaping by interpolating finite impulse response (FIR) filters in conjunction with digital backward propagation (DBP) in coherent 112 Gbit s−1 dual-polarization quadrature phase shift keying (DP-QPSK) transmission. The results depict that RRC pulses are more tolerant to intra-channel non-linearities, i.e. self-phase modulation (SPM), as compared to standard RZ-33 and NRZ pulses. The non-linear threshold point is improved by using RRC pulses by a factor of 2 dB signal input power as compared to RZ pulses and by 4 dB signal launch power as compared to NRZ pulses. The behavior of RRC pulses is also investigated with standard single mode fiber (SMF), non-zero dispersion shifted fiber (NZDSF) and next-generation large Aeff pure silica core fiber (LA-PSCF). Most importantly multi-span DBP is implemented and in the case of RRC pulses the computational efforts of the conventional DBP algorithm are reduced by 80% with a diminutive Q-penalty of 0.74 dB. The duty cycle of the RRC pulses is further optimized for efficient system performance. We have also compared the performance of single-channel transmission with the multi-channel transmission, where the performance is limited due to inter-channel non-linear effects. Furthermore, the non-linear tolerance of RRC pulses is investigated with; (a) different amplifier spacing and (b) variation in transmission link design information for the DBP algorith
UnivIS-Import:2015-04-14:Pub.2012.tech.IE.LEH.applic

Application of selected performance test scenarios on multi-channel UHF receivers - Trommer, Ralph; Quednau, Philipp; Schmidt, Lorenz-Peter (GeMiC 2016 - The 10th German Microwave Conference (GeMiC 2016), 2016)
In a preceding paper a multi-channel test signal generator for UHF radar applications was presented. The present contribution shows the application of this generator to test the performance of multi-channel receivers in selected scenarios. Exemplary measurement results are presented showing the usable dynamic range and the maximum packet reception rate for a secondary surveillance radar receiver and a smart meter data collector. Furthermore the direction-of-arrival estimation precision and the source separation capabilities of the receivers are tested under various conditions.
lhft_intern.bib::Trommer2016a

Application of Silicon Micromachining Techniques for the Manufacturing of New Passive THz-Components - Biber, Stephan; Schür, Jan; Schmidt, Lorenz-Peter (German Microwave Conference, Karlsruhe, March, 2006)
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.applic

Application of state space frequency estimation techniques to radar systems - Gulden, Peter; Vossiek, Martin; Storck, E.; Heide, Patric (IEEE International Conference on Acoustics, Speech, and Signal Processing, 2001)
Many applications for FMCW radar systems require the resolution of several closely spaced frequencies. In general the Fast Fourier Transform (FFT) is used for spectrum estimation, despite the inherent resolution problems. To overcome the resolution limitation the state space approach has been proposed in [1-3]. However, most experimental results in [1-3] are based on simulations. This paper points out the differences of the "real world" signal structure to simulated signals, and describes the problems posed by real radar signals. For one of the key steps of the state space algorithm, model order selection, a novel algorithm based on a posteriori analysis is introduced. The feasibility of the new approach is verified with an actual 24 GHz level gauging FMCW radar system. Our approach yields stable and accurate results with a resolution approximately three times higher than the FFT resolution.
UnivIS-Import:2015-04-16:Pub.2001.tech.IE.LEH.applic

Application of State-Space Frequency Estimation to a 24-GHz FMCW Tank Level Gauging System - Gulden, Peter; Vossiek, Martin; Pichler, Markus; Stelzer, Andreas (33rd European Microwave Conference, EuMC, 2003)
Radar is a well established tank level gauging technique. Today, a shift towards more demanding measurement applications can be observed. As a result, novel radar signal processing algorithms emerge. One of the most challenging tasks for tank level gauging systems is separation of closely spaced targets, especially with the given bandwidth limitations set by both legal means and technical feasibility. Superresolution methods are expected to overcome the inherent resolution limits of Fourier transform based algorithms. However, they are fairly complex, making adaptation to real world radar signals a tedious and complicated task. Furthermore stability problems occur, mainly caused by the necessary a priori model-order estimation. This paper now demonstrates a robust implementation in a commercial 24 GHz radar tank level gauging system, where an adaptive model-order estimation algorithm is used. The measurements in an industrial tank show a threefold increase of the resolution while maintaining stability. Finally a special set of measurements shows that the selected state-space approach is especially well suited for the resolution of small peaks adjacent to larger echoes. © 2003 EUMA.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.applic

Application of the photoelectronic mixing device to optical measurement of presence, distance and velocity - Gulden, Peter; Vossiek, Martin; Heide, Patric; Schwarte, R. (30th European Microwave Conference, EuMC, 2000)
The novel photoelectronic mixing device (PMD) brings about new opportunities in the area of optical 3-D imaging and velocity measurement. This paper reviews the PMD principle and points out the similarities between PMD systems and conventional radar systems. An experimental setup for range measurement with the PMD is shown. For the first time radar modulation techniques have been applied to the PMD device. Experiments stress that they are well suited for 3-D imaging. Previously these modulation concepts were only employed with either radar or sophisticated optical systems. © 2000 IEEE.
UnivIS-Import:2015-04-16:Pub.2000.tech.IE.LEH.applic

Application of the Principal Component Analysis for acceleration based UHF RFID tag tracking - Parr, Andreas; Miesen, Robert; Kirsch, Fabian; Vossiek, Martin (IEEE International Conference on Wireless Information Technology and Systems 2012, 2012)
An algorithm for AoA estimation of UHF RFID tags, based on an acceleration defined synthetic aperture is derived with the aid of the Principal Component Analysis. It gives an analytical solution for the tag direction and requires significantly less computational effort than comparable algorithms while performing nearly as good as the benchmark algorithm. Handheld tracking systems using the proposed algorithm could therefore be implemented with significantly higher cost and power efficiency. © 2012 IEE
UnivIS-Import:2015-04-16:Pub.2012.tech.IE.LEH.applic_8

Applications of Digital Signal Processing - Asif, R; Lin, C; Schmauß, Bernhard (Applications of Digital Signal Processing, 2011)
lhft_intern.bib::Asif2011

A Practical Concept for Precise Calibration of MIMO Radar Systems - Geiß, Johanna; Sippel, Erik; Vossiek, Martin (18th European Radar Conference (EuRAD), 2022)
The calibration of MIMO radar systems is crucial to compensate complex gain and mutual coupling errors of antenna arrays, thereby enabling a good measurement performance. With the increased importance of automotive MIMO radar sensors, there is a need for a reliable calibration procedure with low requirements on the calibration setup and the necessary reference system. Especially concepts for in-situ and re-calibration of already installed radars with deteriorated performance due to aging and/or possible deformation, are required to match the high safety standards in autonomous driving. Recently, we proposed a calibration approach for receive antenna arrays, i.e. SIMO systems, which solely requires relative position information to create a synthetic aperture with the radar. In this paper, this approach is extended to cope with MIMO systems, thereby estimating the mutual coupling matrices associated with the transmit and the receive antenna array. Furthermore, the special case of uniform linear arrays is discussed. The MIMO calibration is successfully validated by measurements with a commercial 76 GHz MIMO radar.<br
Keywords: antenna array; calibration; in-situ calibration; MIMO radar; mutual coupling; sparsity

A PRACTICAL DATA GENERATION FRAMEWORK FOR 4D AUTOMOTIVE MIMO RADAR: ENABLING DEEP LEARNING AND RADAR PERFORMANCE ANALYSIS - Jürgensen, Manuel; Vossiek, Martin; Michel, J.C. Fuentes (The 9th European Congress on Computational Methods in Applied Sciences and Engineering ECCOMAS Congress 2024, 2024)
Radar sensors play a major role in the environmental perception of ADAS [1]. Their robustness in adverse weather conditions particularly differentiates the radar from other sensors used in ADAS, such as camera and lidar [2]. Furthermore, radar sensors are cheaper than lidar sensors, making them feasible for a wide range of applications in vehicles. Due to the physical working principle, radar sensors can achieve accurate measurements in range and velocity. However, in ADAS applications, not only range and velocity measurements but also measurement of the angular position in both the azimuth and elevation domains are crucial. In future applications, radars ought to be able to resolve fine details in the environment, such as Manuel Jürgensen, Martin Vossiek, and Juan Carlos Fuentes Michel vulnerable road users in different situations. Increasing the resolution of radar applications is a field of current research in the ADAS field [3]. Multiple papers have shown that deep learning has great potential in the domain of radar signal processing. In particular, in the case of angular processing, deep neural networks (DNNs) show promising results [4], [5]. DNNs can increase the resolution of different radar sensors using the same hardware and antenna layouts [4]. However, training DNNs relies on labelled data availability. Current datasets on radar data cover only some signal processing steps and sometimes lack annotations [6]. Furthermore, generic radar datasets that can be applicable to different radar systems cannot be retrieved through measurements. This is due to the nature of the radar cube and the information stored within it. Zhou et al. [6] reviewed different radar datasets for diverse types of radar. From an industrial perspective, developing a DNN for detection purposes is reasonable only if the DNN fits the sensor in use. This creates a problem with data collection and labelling. For every new sensor in development, we need to create a new dataset and a new set of labels, which is resource-intensive and time-consuming. A solution to this problem is proposed with a ray tracing simulation based on synthetic environments, in which Schuessler et al. [7] created realistic results in their radar data simulations. However, this approach requires creating artificial scenarios or using pregenerated digital worlds, each presenting its challenges related to realism. Ensuring realistic scenarios and a broad mix of object and scenario types is critical, as is addressing the challenges of simulating radar cross-section (RCS) [6]. In this paper, we present a method for generating datasets that are partly synthetic and partly data-driven. We use recorded detections from a production high-resolution (HR) radar sensor and accumulate them over consecutive radar cycles to increase the resolution. For our raw radar spectrum simulation, we treat each accumulated detection as a scatter centre and generate a sine wave in the intermediate frequency (IF) domain. Our signal processing framework then processes the raw spectrum, computes range and velocity fast Fourier transform (FFT), performs beamforming, and determines the local maxima through a constant false alarm rate (CFAR) algorithm. In this way, we generate every step of the radar data cube that is of interest for radar performance analysis. Our framework’s advantages lie in the practicability and versatility of the approach. According to our findings, our approach has proven to be economical in the predevelopment of radar and in generating data for possible use in deep learning applications. <br
Keywords: Radar; Deep Learning; Data-driven Methods; Physics-based Methods

A Pseudo-Random Noise-Coded 1.35 GHz Sequential Sampling Impulse Radar System for Forefield Reconnaissance for Ice Exploration Melting Probes - Haberberger, Niklas; Stelzig, Michael; Krabbe, Lena; Hehn, Markus; Vossiek, Martin (2024 21st European Radar Conference (EuRAD), 2024)
Presented in this study is a sequential sampling impulse radar (SSIR) system with pseudo-random noise (PRN) coding designed for forefield reconnaissance for melting probes, enabling the subsurface exploration of icy moons, such as Europa and Enceladus. Characterized by simple hardware and a compact form factor, the developed multi-channel SSIR utilizes pseudo-random noise sequences to effectively enhance the signal-to-noise ratio (SNR). Demonstrating exceptional sensitivity and performance, a prototype system was tested on the Langenferner glacier in Ital

A Pulsed Frequency Modulated Ultra Wideband Technique for Indoor Positioning Systems - Waldmann, Benjamin; Gulden, Peter; Vossiek, Martin; Weigel, Robert (Frequenz, 2008)
In this paper a novel approach for a high precision local positioning radar using an ultra wideband technique is presented. The concept is based on the standard FMCW (frequency modulated continuous wave) radar principle combined with short pulses to fulfill the emission limits given by the official regulatory authorities. Besides the well knowen advantages ifa FMCW radar the proposed system implies a wide frequency bandwidth. With this concept, a high accuracy in dense multipath indoor environments can be achieved, ideally suited for 1D, 2D, and 3D localization. A prototype was fabricated which operates at the center frequency of 7.5 GHz utilizing a bandwidth of 1 GHz. With the setup presented in this paper the distance between two wireless units can be measured achieving a low standard deviation.
elib2cris::1512001600,waldmann2008
Keywords: FMCW; Indoor navigation; Radar position measurement; Ultra wideband

A Quasi-Lumped Ultra Broadband Contiguos SSL-Diplexer from DC to 80 GHz - Rehner, Robert; Sterns, Michael; Schneiderbanger, Dirk; Martius, Siegfried; Schmidt, Lorenz-Peter (IMS 2009, Boston, June, 2009)
A contiguous planar diplexer in suspended stripline technology with ultrawideband channels from DC to 40 GHz and 40 GHz to 80 GHz is presented. The design of the diplexer is based on quasi-complementary LC lowpass and highpass prototypes which are directly transformed into transmission line elements by using a quasi-lumped approach. This very straightforward design procedure requires no susceptance annulling networks and no introduction of unit elements which could limit the diplexer's operation bandwidth. For achieving an optimal compatibility with external circuits, an ultra-broadband SSL-MSL (suspended stripline - microstrip line) transition with a return loss of more than 18 dB from DC to 83 GHz was designed. The realized diplexer is extremely compact (6times4.5mm) and features a return loss of more than 12 dB from DC to 81 GHz with very low channel insertion losses of typically less than 1 dB after proper optimization.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.aquasi

A Quasioptical Bandpass Filter for 300 GHz on an Electrically thick Silicon Substrate - Biber, Stephan; Bozzi, M.; Günther, O.; Perregrini, L.; Schmidt, Lorenz-Peter (International Microwave Symposium IMS, Long Beach, USA, June, 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.aquasi

A Radar and Sonar-Based Hybrid Forefield Reconnaissance System for Melting Probes for Englacial Exploration - Stelzig, Michael; Haberberger, Niklas; Audehm, Jan; Becker, Fabian; Nghê, Chi Thanh; Ellinger, Enrico; Do, Mia; Krabbe, Lena; Heinen, Dirk; Zierke, Simon; Böck, Georg; Helbing, Klaus; et al. (IEEE Transactions on Geoscience and Remote Sensing, 2024)
The polar regions of Mars as well as the ice-covered moons such as Saturn’s Enceladus and Jupiter’s Europa have emerged as significant targets for ongoing and future space missions focused on investigating potentially habitable celestial bodies within our solar system. A key objective of these missions is to explore subglacial water reservoirs lying beneath the ice crusts of moons, such as Europa. The utilization of melting probes shows immense promise for achieving this goal. However, in addition to the capability to melt through the ice body, such a probe must also be able to identify the ice–water interface as well as obstacles in its path, such as cavities or meteoric rocks. To address these challenges, we present a forefield reconnaissance system (FRS) featuring a hybrid sensing approach that combines radar and sonar both integrated into the tip of a melting probe. Furthermore, the system includes an in situ permittivity sensor to ensure accurate radar range assignment and to gather scientific data about the ice body. The system has been integrated into a demonstrator melting probe and tested in a terrestrial analog scenario. Measurements at the Jungfraufirn in Switzerland confirm the potential of the developed system.<br
Keywords: Probes; Radar; Reservoirs; Sonar; Heating systems; Snow; Permittivity; Radar System; Solar System; Thermal Conductivity; Dielectric Constant; Autonomous Vehicles; Acoustic Signals; Inertial Measurement Unit; Vector Network Analyzer; Phase-locked Loop; Simultaneous Localization And Mapping; Planar Antenna; Gallium Nitride; Robot Operating System; Ground Penetrating Radar; Aluminum Nitride; Coaxial Line; German Aerospace Center; High Power Amplifier; Protection Circuit; Outer Conductor; Relative Permittivity Values; Acoustic Transducer; Extraterrestrial Life; Binary Phase Shift Keying; Stray Field; Echo Signal; Test Locations; Antenna Array; Radar Measurements; Equivalent Circuit

A Radar-Based Concept for Simultaneous High-Resolution Imaging and Pixel-Wise Velocity Analysis for Tracking Human Motion - Bräunig, Johanna; Heinrich, Simon; Coppers, Birte; Kammel, Christoph; Wirth, Vanessa; Stamminger, Marc; Leyendecker, Sigrid; Liphardt, Anna-Maria; Ullmann, Ingrid; Vossiek, Martin (IEEE Journal of Microwaves, 2024)
The radar-based analysis of human motion is actively being researched due to its contact- and markerless nature and ability to measure motion directly via the Doppler effect. Especially in medical and biomechanical fields, precise movement analysis is crucial. However, existing radar-based studies typically exhibit low lateral resolution, focusing on velocity evaluations and the tracking of scattering centers resolvable in the range or Doppler domains. In this work, we present a novel concept that enables a pixel-wise velocity analysis of human motion in radar near-field imaging scenarios. For this, we utilize the well-established back-projection technique to reconstruct consecutive radar images and perform a subsequent pixel-wise phase comparison. To accurately capture pixel-specific velocities along the depth dimension, this is followed by corrections of near-field geometry distortions accounting for aperture properties and pixel positions. Our theoretical derivations are supported by comprehensive point target simulations. To assess the performance of the proposed approach, we conducted a proof-of-concept study. We tracked a hand surface's movement while performing a finger tapping motion and compared the fingertip position and velocity determined by the radar with the respective values obtained from an optical marker-based system. The results showed a velocity measurement accuracy of 8.1mms−1 and a tracking accuracy of 1.4mm , demonstrating the great potential of our approach. The high angular resolution of the velocity measurement enables the tracking of the entire illuminated body shell, extending the range of future applications of radar-based motion analysis.<br
Keywords: Radar tracking; Radar; Radar imaging; Radar antennas; MIMO radar; Velocity measurement; Target tracking; Doppler radar; Signal resolution; Scattering; Human motion tracking; near-field imaging; radar imaging; velocity measurement

A Realistic Radar Ray Tracing Simulator for Hand Pose Imaging - Bräunig, Johanna; Schüßler, Christian; Wirth, Vanessa; Stamminger, Marc; Ullmann, Ingrid; Vossiek, Martin (EuRAD 2023, 2023)
With the increasing popularity of human-computer interaction applications, there is also growing interest in generating sufficiently large and diverse data sets for automatic radar-based recognition of hand poses and gestures. Radar simulations are a vital approach to generating training data (e.g., for machine learning). Therefore, this work applies a ray tracing method to radar imaging of the hand. The performance of the proposed simulation approach is verified by a comparison of simulation and measurement data based on an imaging radar with a high lateral resolution. In addition, the surface material model incorporated into the ray tracer is highlighted in more detail and parameterized for radar hand imaging. Measurements and simulations show a very high similarity between synthetic and real radar image captures. The presented results demonstrate that it is possible to generate very realistic simulations of radar measurement data even for complex radar hand pose imaging systems. <br
Keywords: radar simulation; ray tracing; radar imaging; human-computer interaction; hand pose recognition.

A Realistic Radar Ray Tracing Simulator for Large MIMO-Arrays in Automotive Environments - Schüßler, Christian; Hoffmann, Marcel; Bräunig, Johanna; Ullmann, Ingrid; Ebelt, Randolf; Vossiek, Martin (IEEE Journal of Microwaves, 2021)
With the rise of high resolution multiple input multiple output (MIMO) systems, radar became an important sensor in the development of Advanced Driver Assistance Systems (ADAS) and autonomous driving applications. Autonomous driving will rely strongly on artificial intelligence. Since most modern classification algorithms are based on neural networks, they require huge amounts of data to perform well, especially in unexpected traffic situations. Radar sensor simulation can potentially produce a great variety of training data for machine learning algorithms, which makes it an important cornerstone in the development of ADAS. Furthermore, with radar simulators, different antenna configurations and various edge cases can be simulated. In this work, a versatile ray tracing toolchain based on the shoot and bouncing rays (SBR) approach is presented. The program is able to simulate complex urban environments including realistic clutter, by utilizing simplistic reflection models. The program does not only produce realistic radar images, but also generates camera-like images using the same materials. Furthermore, this work deals with the adaption of the SBR method to radar sensors with an arbitrary number of transmit (TX)- and receive (RX) antennas, which enables the simulation of large MIMO arrays. A novel performance optimization approach is proposed for large numbers of TX antennas, which reduces the runtime dramatically. The quality of the simulation is verified by measuring a complex and realistic scenario with a high resolution automotive MIMO radar. Also, a study of the effect on quality and runtime is being investigated for various optimization approaches, including the proposed method.
Keywords: Radar; Radar antennas; Solid modeling; Computational modeling; Antennas; Scattering; Radar cross-sections; MIMO radar; radar simulation; ray tracing; shoot and bouncing rays

A Real-Time UWB Multi-Channel Indoor Positioning System for Industrial Scenarios - Schröer, Guido (2018 NINTH INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION (IPIN 2018), 2018)
CRIS-Team WoS Importer:2019-11-26

Are odorant constituents of herbal tea transferred into human milk? - Denzer, Melanie; Kirsch, Fabian; Büttner, Andrea (Journal of Agricultural and Food Chemistry, 2015)

A Review and Tutorial on Machine Learning- Enabled Radar-Based Biomedical Monitoring - Krauß, Daniel; Engel, Lukas; Ott, Tabea; Bräunig, Johanna; Richer, Robert; Gambietz, Markus; Albrecht, Nils; Hille, Eva M; Ullmann, Ingrid; Braun, Matthias; Dabrock, Peter; Kölpin, Alexander; et al. (IEEE Open Journal of Engineering in Medicine and Biology, 2024)
Radio detection and ranging-based (radar) sensing offers unique opportunities for biomedical monitoring and can help overcome the limitations of currently established solutions. Due to its contactless and unobtrusive measurement principle, it can facilitate the longitudinal recording of human physiology and can help to bridge the gap from laboratory to real-world assessments. However, radar sensors typically yield complex and multidimensional data that are hard to interpret without domain expertise. Machine learning (ML) algorithms can be trained to extract meaningful information from radar data for medical experts, enhancing not only diagnostic capabilities but also contributing to advancements in disease prevention and treatment. However, until now, the two aspects of radar-based data acquisition and ML-based data processing have mostly been addressed individually and not as part of a holistic and end-to-end data analysis pipeline. For this reason, we present a tutorial on radar-based ML applications for biomedical monitoring that equally emphasizes both dimensions. We highlight the fundamentals of radar and ML theory, data acquisition and representation and outline categories of clinical relevance. Since the contactless and unobtrusive nature of radar-based sensing also raises novel ethical concerns regarding biomedical monitoring, we additionally present a discussion that carefully addresses the ethical aspects of this novel technology, particularly regarding data privacy, ownership, and potential biases in ML algorithms.
Keywords: Radar; Biomedical monitoring; Doppler effect; Doppler radar; Sensors; Radar measurements; Radar applications; Radar; Machine Learning; Medicine; Ethics; Biomedical Monitoring

A Review on Ultrasound-based Methods to Image the Distribution of Magnetic Nanoparticles in Biomedical Applications - Huber, Christian; Pavan, Theo Z.; Ullmann, Ingrid; Heim, Christian; Rupitsch, Stefan J.; Vossiek, Martin; Alexiou, Christoph; Ermert, Helmut; Lyer, Stefan (Ultrasound in Medicine and Biology, 2024)
Magnetic nanoparticles (MNPs) have gained significant attention in biomedical engineering and imaging applications due to their unique magnetic and mechanical properties. With their high magnetization and small size, MNPs serve as excitation sources for magnetically heating to destroy tumors (magnetic hyperthermia) and magnetically controlled drug carriers in magnetic drug targeting. However, effectively visualizing the distribution of MNPs during research or potential clinical use with low-cost modalities remains a critical challenge. Although magnetic resonance imaging provides pre- and post-procedural imaging, it is considered to be high cost, and real-time imaging during clinical procedures is limited. In contrast, ultrasound-based imaging methods offer the advantage of providing the potential for immediate feedback during clinical use and are considered to be a low-cost modality. Ultrasound-based imaging techniques, including magnetomotive ultrasound, magnetoacoustic tomography, and thermoacoustic imaging, emerged as promising approaches for imaging the distribution of MNPs. These techniques offer the potential for real-time imaging, facilitating precise therapy monitoring. By exploring the strengths and limitations of various ultrasound-based imaging techniques for MNPs, this review seeks to provide comprehensive insights that can guide researchers in selecting suitable ultrasound-based modalities and inspire further advancements in this exciting field.
CRIS-Team Scopus Importer:2024-11-22
Keywords: Magnetic nanoparticles; Magnetoacoustic tomography; Magnetomotive ultrasound; Thermoacoustic imaging; Tomography; Ultrasound-based imaging

A Robust Air-Coupled Ultrasonic Piezoelectric-Carbon-Fiber-Reinforced-PolymerTransducer for Mobile Robot Navigation - Flores, Sergio Alberto; Vossiek, Martin (International Ultrasonics Symposium 2014, 2014)
lhft_intern.bib::Flores2014

A robust real-time demodulation scheme for backscatter transponder based wireless positioning systems - Schütz, Martin; Vossiek, Martin (GeMiC 2018 - The 11th German Microwave Conference (GeMiC 2018), 2018)
In this paper, we present a robust algorithm for demodulation and evaluation of backscatter transponder induced beat signals in wireless positioning systems. In particular, an analysis filter bank based on Goertzel filter is used for signal detection. A particle swarm optimizer controls the configuration of the filter bank and is used to measure the range of the transponder based on spectral evaluation of the beat signal with very high resolution. A Kalman-Filter is applied for optimum estimation of the range with noise suppression. An implementation and system demonstrator based on an heterogeneous FPGA and software implementation with an FMCW radar is presented to evince the proposed demodulation scheme. It allows gapless processing in chirp sequence radar systems and high output rates with high resolution and low nois
lhft_intern.bib::schuetz18

A rotating synthetic aperture radar imaging concept for robot navigation - Ali, Faiza; Bauer, Georg; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2014)
This paper introduces a concept for robot navigation based on a rotating synthetic aperture short-range radar scanner. It uses an innovative broadband holographic reconstruction algorithm, which overcomes the typical problem of residual phase errors caused by an imprecisely measured aperture position and moving targets. Thus, it is no longer necessary to know the exact trajectory of the synthetic aperture radar to get a high-resolution image, which is a major advantage over the classical holographic reconstruction algorithm. However, the developed algorithm is not only used to compute a high-resolution 360° 2-D image after each turn of the radar platform while the robot is moving, but also to calculate the relative residual radial velocity between the moving radar scanner system and all targets in the environment. This allows us to determine the exact velocity of the robotic system on which the radar scanner is mounted, and thus to obtain the exact radar trajectory, if there are stationary targets like walls in the environment. © 1963-2012 IEEE.
Keywords: Mobile robots; navigation; radar imaging; synthetic aperture radar (SAR); velocity measurement

A Scalable and Cost-Efficient Antenna Testbed Using FPGA-Server Compound Structures for Prototyping 6G Applications - Neu, Marc; Karle, Christian; Nuss, Benjamin; Gröschel, Patrick; Becker, Juergen (Proceedings - 19th International Conference on Distributed Computing in Smart Systems and the Internet of Things, DCOSS-IoT 2023, 2023)
Developing the sixth generation mobile network infrastructure is expected to utilize mm-Wave technology and multiple-input multiple-output (MIMO) arrays to enable high-speed, low-latency communication. Designing suitable MIMO arrays that support multi-GHz bandwidths per channel imposes enormous requirements on all sub-components performing analog-digital conversion, data acquisition, and digital signal processing. Current MIMO testbeds lack the bandwidth and radio-frequency sampling rates of future mobile network applications. Therefore, we propose a cost-efficient architecture based on off-the-shelf components that is scalable in the number of antennas per testbed and the attainable bandwidth per channel. We demonstrate the feasibility of our approach by implementing two testbeds and transmitting a broadband orthogonal frequency-division multiplexing signal over concurrent channels. In comparison to current MIMO testbeds, we support 2.46 times higher bandwidths per channel and 9.84 times higher radio-frequency sampling rates, which we demonstrate by performing infield measurements. To conclude, our testbed allows for the proto-typing of broadband MIMO antennas, forming the foundation for cost-efficient evaluation of novel communication protocols in large test fields.
CRIS-Team Scopus Importer:2023-10-27
Keywords: 6G; FPGA; MIMO; Prototyping; Testbed

A Secondary Surveillance Radar with Miniaturized Transponders for Localization of Small-Sized UAVs in Controlled Air Space - Schütz, Martin; Dobrev, Yassen; Pavlenko, Tatiana; Vossiek, Martin (2018 IEEE International Workshop on Metrology for Aerospace (MetroAeroSpace), 2018)
This paper presents a concept study of a novel, compact secondary surveillance radar for localization and identification of small-sized, unmanned aerial vehicles (UAV) in controlled air space. For high-precision localization, a UAV can be equipped with miniaturized backscatter transponders like it is common practice in civil and military aviation. They further allow transmitting arbitrary data to the surveillance radar which can be used for friend-or-foe identification. To demonstrate the concept, a 24 GHz multichannel radar system is used in combination with a appropriate transponder based on the switched injection-locked oscillator (SILO) concept. We show a measurement to estimate the position and radial velocity of a small quadrocopter UAV. The presented system results from the project VaMEx-LAOLa, where a local ad-hoc localization and landing system for UAVs is develope
lhft_intern.bib::schuetz18c

A Short Range Synthetic Aperture Imaging Radar with Rotating Antenna - Ali, Faiza; Urban, Alexander; Vossiek, Martin (International Journal of Electronics and Telecommunications, 2011)
The design of a short range synthetic aperture imaging radar is introduced in this paper. A radar hologram is acquired using a small omnidirectional antenna that is mounted on a rotating platform. After each turn of the platform a high resolution 360° 2D image is reconstructed; a rotating window function optimizes the reconstructed image function to get the best image focus for detecting both weak and strong scatterers. The rotating window function depends on the target direction and is executed for each image point and each target direction. The size of the synthetic aperture - and thus the lateral resolution of the imaging system - is determined by the diameter of the circular antenna trajectory. In contrast to common radar scanner concepts that utilize highly directional and thus bulky antennas, the proposed scanner concept has the advantage of using a small, lightweight omni-directional antenna. The developed radar system is much more compact and the scanning mechanics are significantly simplified. Furthermore, an omni-directional antenna offers very straightforward options for powering the radar on the rotation platform. Measurement results obtained with a 24 GHz FMCW short range radar sensor illustrate the performance of the proposed SAR imaging metho
lhft_intern.bib::Ali2011

A Simple and Low-Cost Technique to Measure the Magnetic Susceptibility of Ferrofluids - Thalmayer, Angelika; Xiao, Keyu; Lübke, Maximilian; Borin, Dmitry; Odenbach, Stefan; Unterweger, Harald; Helmreich, Klaus; Fischer, Georg (IEEE Sensors, 2023)

A Simple and Versatile Concept to Improve Dynamic Range and Enable Target Angle Adaptability in Radar Target Simulators - Birkenhauer, Christoph; Körner, Georg; Stief, Patrick; Hamberger, Gerhard; Beer, Matthias; Carlowitz, Christian; Vossiek, Martin (IEEE Journal of Microwaves, 2023)
Radar target simulators are not only a critical tool for verifying and testing radar systems but also play an important role in supporting the development of self-driving cars. Advances in radar sensors and techniques raise the required specifications for these units, increasing their complexity and cost. This article presents a novel and universal concept for radar target simulators that addresses these issues by responding only to the transmitted signal of a radar sensor during a fraction of the time, therefore modulating the average of the signal. This offers advantages for three independent use cases, which may be combined. First, the dynamic range and resolution of simulated target echo power can be improved even for existing systems. Second, the simulation of multiangle scenarios with a single backend is possible with this approach. Finally, hardware complexity and power consumption can be reduced. The proposed concept is examined extensively for frequency-modulated continuous wave radar, and design decisions are made. The theoretical considerations are validated with measurements with a real radar target simulator showing an improvement of up to 30dB in the dynamic range with no observable negative side effects.<br
Keywords: Radar; Modulation; Dynamic range; Radar cross-sections; Switches; Radar antennas; Sensors

A Simplified Method for Measuring Complex S-Parameters Dedicated to Synthetic Instrumentation - Schramm, Marcus; Hrobak, Michael; Schür, Jan; Schmidt, Lorenz-Peter; Lechner, A. (EUMW / EUMC, Paris, October, 2010)
The constantly emerging market for high and medium volume test applications in the area of high frequency devices calls for cost efficient test solutions. One way to achieve this is using modular reconfigurable measurement equipment, thus enabling the reuse of hardware. This tendency brought up some synthetic instruments capable of sophisticated high frequency measurements up to 6 GHz. One feature those COTS-(Commercial Off The Shelf) systems are lacking, is the ability to measure complex scattering parameters. This article introduces an architecture of a synthetic VNA (Vector Network Analyzer) that enables a cost efficient way of measuring S-Parameters. The theoretical basics, a simulation based accuracy estimation as well as first measurement results are presented as proof of concept.
lhft_intern.bib::Schramm10

A Small Size Low Cost Electronically Tunable Bandpass Filter with Integrated Bias Control - Quednau, Philipp; Trommer, Ralph; Schmidt, Lorenz-Peter (International IEEE Conference on Microwaves, Communications, Antennas and Electronic Systems 2013, 2013)
This paper presents the development of a compact sized, low cost wide range tunable bandpass filter based on a novel RF structure. The proposed design offers a narrow passband with a relative bandwidth down to 3.9 %, a wide tuning range from 700 MHz to 1150 MHz and the ability to adapt bandwidth and insertion loss during operation. Tuning is achieved by reverse biased varactor diodes with a low supply voltage of 5 V max. Design of the novel bandpass structure, integration and miniaturization to reduce its size down to approx. 6 cm 2 is discussed. Measurement results over the whole tuning range are presented and the design of a miniaturized multi channel bias controller for easy frequency setting and temperature compensation is described. © 2013 IEEE.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.asmall

A SOLR calibration procedure for the 16-term error model - Schramm, Marcus; Hrobak, Michael; Schür, Jan; Schmidt, Lorenz-Peter (42th European Microwave Week, 2012)
Scattering parameter measurements in the presence of crosstalk is a well documented problem. The available calibration methods, suited for the general 16-term error model, capable of taking the crosstalk into account, suffer from the required Thru-Standard, which has to be perfectly known. This information is hard to acquire in some cases. An approach which makes the advantage of the 7-term SOLR (Short-Open-Load-Reciprocal) accessible to the 16-term error model is discussed in this article. The mathematical description, the feasibility for multiport applications, measurement results and a brief sensitivity analysis will be presented.
lhft_intern.bib::Schramm2012

Assessment of OFDM Radar in Automotive and Joint Communication and Sensing Scenarios using Realistic Ray Tracing Simulations - Noegel, Theresa; Sura, Oliver; Schüßler, Christian; Hoffmann, Marcel; Vossiek, Martin (ICMIM 2024: International Conference on Microwaves for Intelligent Mobility - 7th IEEE MTT Conference, 2024)
In the context of autonomous driving and next-generation wireless communication, Joint Communication and Sensing (JCAS) with Orthogonal Frequency Division Multiplexing (OFDM) signals is emerging. This development can be significantly accelerated through realistic radar simulations. Therefore, we extended an advanced radar ray tracing simulator, currently deployed for Frequency-Modulated Continuous Wave (FMCW) simulations, to encompass the OFDM signal model. To validate its functionality, we conducted simulations of both FMCW and OFDM signals in the same virtual scene using comparable digital radar twins. Given our previous demonstration that FMCW simulations closely resemble real-world measurements, the OFDM simulations can also be considered realistic. Consequently, the proposed method is a promising tool to enhance the development and to enable the optimization of radar-based OFDM applications.
CRIS-Team Scopus Importer:2024-09-06

A Subharmonic Super-Regenerative FMCW Radar With Improved Intermodulation Efficiency for Applications Beyond Cut-Off Frequency - Hahn, Leonhard; Vossiek, Martin; Carlowitz, Christian (IEEE Transactions on Microwave Theory and Techniques, 2023)
This article presents a novel subharmonic super-regenerative receiver (SHSRR) radar for high-sensitivity and low-noise operation in beyond- fmax frequency-modulated continuous wave (FMCW) applications. In contrast to conventional super-regenerative designs, the proposed concept is extended by an inherently implemented, subharmonic downconversion. This downconversion allows a tripling of both operation frequency and bandwidth and thereby enables the system’s operation beyond its gain limit. Operated with the novel SHSRR, the maximum operating frequency and bandwidth of FMCW transceivers is proven to be significantly increased. With local oscillator (LO) power requirements considerably reduced compared with passive mixer approaches, the concept is also suited for massive multichannel scaling. Optimized modulation signals are applied to the SHSRR concept, which intentionally boost the receiver’s nonlinearity and thus substantially improve previously achieved intermodulation efficiencies for the first time. The concept is verified experimentally with a 24-GHz FMCW radar transceiver implemented in planar microstrip technology. Due to the introduced optimization approach, extremely high sensitivity levels of well below −114 dBm have been accomplished, whereby the previously achieved noise figure is improved from almost 30 dB down to 11 dB. Power consumption was limited to 9 mW. This simple, novel concept is thus suitable for scaling to integrated circuits with a high number of receive channels at several 100-GHz carrier frequencies.<br
Keywords: Sensitivity; Receivers; Radio frequency; Oscillators; Modulation; Frequency modulation; Optimization

a)Submikrowellenelektronik - Neue Technologieforschung fuer interdisziplinäre Grenzbereiche - Brand, Hans (1986)
lhft_intern.bib::thirty_years_LHFT_239

A Survey on Radar-Based Continuous Human Activity Recognition - Ullmann, Ingrid; Guendel, Ronny; Kruse, Nicolas Christian; Fioranelli, Francesco; Yarovoy, Alexander (IEEE Journal of Microwaves, 2023)
Radar-based human motion and activity recognition is currently a topic of great research interest, as the aging population increases and older individuals prefer an independent lifestyle. This technology has a wide range of applications, such as fall detection in assisted living, gesture recognition for human-machine interfaces, and many more. Numerous studies exist on various approaches for radar-based activity capture and classification. However, most of these employ rather artificial data, often obtained in laboratory environments, and typically collected under particular conditions. Specifically, most research so far has aimed at distinguishing a predefined set of single activities with a defined start, stop and duration. This paper aims at drawing the attention to a so far less researched issue, one that will be of vital importance for future real-world application of radar-based human activity recognition: continuous activity recognition, i.e. recognizing specific activities in a stream of several sequential activities with unknown duration and arbitrary transitions between different classes of activities. A review on the current state of the art in this relatively new topic is given, followed by a discussion on future research directions.<br

A Synthetic Aperture Imaging Concept for a Sequential Sampling Impulse Radar - Krabbe, Lena; Haberberger, Niklas; Stelzig, Michael; Hehn, Markus; Vossiek, Martin (German Microwave Conference (GeMiC), 2024)
Sequential sampling impulse radar, which is known for its low complexity and potential energy efficiency, has seen limited exploration of its imaging capabilities, particularly for synthetic aperture radar (SAR) focusing. This paper fills this gap by introducing a phase-based SAR imaging concept for a sequential sampling impulse radar without IQ-mixer. This work outlines a mathematical model for the received echo signal and processing steps to extract the phase information from the real-valued radar data. Experimental validation is performed in an outdoor scenario. The measurement results demonstrate successful phase-based SAR focusing, overcoming the limitations of amplitude-based reconstruction. The signal processing and imaging concept shown in this paper, combined with the used 1.35 GHz sequential sampling impulse radar systems, is intended for future use in glaciological research for the enhanced monitoring of glacier stratification, but it is also suitable for many other high-resolution ground penetrating radar (GPR) applications.<br
Keywords: synthetic aperture radar; sequential sampling impulse radar; switched oscillators; backprojection

A System Concept for Online Calibration of Massive MIMO Transceiver Arrays for Communication and Localization - Gröschel, Patrick; Zarei, Shahram; Carlowitz, Christian; Lipka, Melanie; Sippel, Erik; Ali, Arslan; Weigel, Robert; Schober, Robert; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2017)
Massive multiple-input multiple-output (MIMO) techniques are being considered for the fifth generation (5G) mobile communication systems in order to deliver high multiplexing gain. However, hardware impairments like quadrature imbalance in mixers violate the requirement for channel reciprocity and may change, e.g., with temperature or while aging. In addition, advanced wireless localization techniques and the generation of predefined beam patterns require knowledge about all antenna phase center positions and the time and phase delay of all transmit and receive channels. Thus, an efficient online compensation method is needed that scales well for very large numbers of transceiver modules. We propose to extend the transmitter with a small measurement feature at the transmitter output based on one uncalibrated power detector per module as well as a single, external four-element backscatter array for the entire matrix. These enhancements facilitate a fast and efficient iterative calibration, which recognizes and mitigates all major error sources. Beside optimal communication throughput and energy efficiency, it thereby brings localization capabilities to mobile networks as an additional major benefit. For verification, a system of multiple cost-efficient 5.8-GHz massive MIMO transceivers with 150-MHz bandwidth and a backscatter array has been implemented. Measurement results demonstrate the capability of the proposed concept to efficiently compensate major error sources as well as its robustness.
elib2cris::1512001600,groeschel2017
Keywords: Backscatter transponder (BT); calibration; fifth generation (5G) mobile communication; massive multiple-input multiple-output (MIMO); wireless localization

A Technology Demonstrator for a 0.5 m x 0.5m Fully Electronic Digital Beamforming mm-Wave Imaging System - Schießl, Andreas; Ahmed, S. S.; Genghammer, A.; Schmidt, Lorenz-Peter (EuCAP 2011, 2011)
This paper describes a demonstrator for a millimeter-wave imaging system, showing for the first time the feasibility of an active fully electronic imaging system in the 80 GHz region using a 2D planar sparse array as an imaging sensor. The demonstrator is capable of capturing images of living persons. In this work, the requirements regarding measurement speed are derived. The system architecture is described in detail using block diagrams. The reference channel concept, the signal distribution network, the modular architecture and the ADC / signal processing concepts are explained. Selected measurement results of key system parameters are presented. mm-Wave images of living persons are shown, including examples demonstrating the effects of movement during the measurement.
lhft_intern.bib::Schiessl11a

A Transmission Method for Conductivity Extraction of Printed Silver Ink - Ehrngruber, Michael; Neermann, Simone; Gold, Gerald (IEEE, 2022)
This paper presents a measurement method being capable of characterizing impact from sintering on reached electrical conductivity of nano silver inks. Therefore, a measurement setup at relatively low frequencies was chosen, so that the electromagnetic (EM) field completely penetrates the conductive region. Thus, the transmission which is highly influenced by the conductivity variations of the material under test can be measured. Even small variations due to different sintering temperatures are measurable in this way. A model describing the transmission of the EM-field through the material sample including a carrier layer of polyimide was set up, which allows for inferring the conductivity of the sample. As samples sputtered copper layers are examined, as well as nano silver inks sintered at different temperatures and with different sintering methods.
Keywords: conductivity measurement; silver ink; material characterization; transmission; 3D printing

A Tutorial on the Sequential Sampling Impulse Radar Concept and Selected Applications - Vossiek, Martin; Haberberger, Niklas; Krabbe, Lena; Hehn, Markus; Carlowitz, Christian; Stelzig, Michael (IEEE Journal of Microwaves, 2023)
The sequential sampling impulse radar is a radar concept that has been known for a very long time. Ultrawideband (UWB) radar systems have been realized based on this concept long before the popular phrases UWB and UWB radar were created. Its hardware simplicity, low cost, potentially high bandwidth and high range resolution, as well as the unsurpassed low power consumption of some of its variants have made it one of the most widely used radar concepts in industrial automation today. Despite its widespread use in practice, however, there are only few publications, textbooks and tutorials that describe this concept in detail and all its varieties and aspects. Especially, the correlation properties and the resulting signal-tonoise ratio (SNR), as well as the phase injection locking of pulsed oscillators, that is required for powerefficient options, have rarely been described in detail. This tutorial introduces the typical sequential sampling impulse radar concept step by step and presents the characteristics and pros and cons. As for the correlation properties and the SNR, the concepts are compared to those of standard coherent impulse radar systems and of frequency modulated continuous wave (FMCW) radar. In addition to the system theory, selected applications are presented to illustrate the attractiveness and elegance, but also the limits, of this interesting and important radar concept. The shown applications range from those in the main field of use of this type of radar, that is, industrial automation, to former and current radar concepts in the areas of automotive radar, ground penetrating radar (GPR), security scanners, and biomedical radar system
Keywords: Ground penetrating radar; Power demand; Costs; Radar measurements; Tutorials; Radar imaging; Radar tracking

A UAV-based Radar Sounder SAR System for the Imaging of Internal Snow and Firn Stratifications - Stelzig, Michael; Benedikter, Andreas; Krabbe, Lena; Schultz, Jakob; Haberberger, Niklas; Braun, Matthias; Krieger, Gerhard; Vossiek, Martin (Proceedings of the European Conference on Synthetic Aperture Radar, EUSAR, 2024)
Unpiloted aerial vehicle (UAV)-based synthetic aperture radars (SAR) offer great potential for use in the structural mapping of snow and firn structures, such as crevasses or stratifications within the subsurface of alpine glaciers. Especially advantageous is the possibility to conduct autonomous and wide-area measurements of a glacier without the risk of crevasse fall or avalanches for ground-penetrating radar (GPR) operators. We present an imaging approach for the mapping of snow and firn structures based on a UAV-borne GPR system, capable of precisely accommodating the refraction effects at the surface. Several common methods for estimating the refraction at the dielectric interface for a planar surface are presented, and their performance is evaluated. As the topography of an alpine glacier is rarely planar, an imaging approach for arbitrary surfaces is presented, which relies on the extraction of the surface from the raw radar B-scan. Measurements from a sand pit experiment confirm the applicability of the imaging approach before the algorithm is applied to measurements from the Jungfraufirn glacier, Switzerland, highlighting the great potential of UAV-based GPR for use in future glacial research.
CRIS-Team Scopus Importer:2024-05-31

Auch Wissenschaft braucht Strom - Brand, Hans (2013)
lhft_intern.bib::Brand2013a

Aufbau einer fliegenden Messplattform mit prziser Flugbahnbestimmungzur Vermessung von Feldstrkeverteilungen - Kirsch, Fabian; Schinke, Tim; Schrader, Thorsten; Vossiek, Martin (Jahrestagung des U.R.S.I. Landesausschuss in der Bundesrepublik Deutschland e.V., 2012)
lhft_intern.bib::Kirsch2012a

Augmented Reality Assisted Handheld for UHF RFID Direction-of-Arrival Estimation - Parr, Andreas; Miesen, Robert; Vossiek, Martin (IEEE RFID 2014, 2014)
lhft_intern.bib::Parr2014a

Ausnutzung von Fasernichtlinearitäten zur Regeneration von hochbitratigen optischen Datensignalen - Striegler, Arne; Schmauß, Bernhard (ITG Fachtagung Kommunikationskabelnetze, Köln, Dezember, 2003)
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.ausnut

Autofocus-Based Estimation of Penetration Depth and Permittivity of Ice Volumes and Snow Using Single SAR Images - Benedikter, Andreas; Rodríguez-Cassolà, Marc; Betancourt-Payan, Felipe; Krieger, Gerhard; Moreira, Alberto (IEEE Transactions on Geoscience and Remote Sensing, 2021)
An intrinsic challenge in the geophysical interpretation of low-frequency SAR imagery of semi-transparent media, such as ice sheets, is the position ambiguity of the scattering structures within the glacial volume. Commonly tackled by applying interferometric and tomographic techniques, their spaceborne implementation exhibits by orders higher complexity compared to missions relying on single SAR images, making them cost expensive or, in the context of planetary missions, even impossible due to limited navigation capability. Besides, even these sophisticated techniques are commonly biased due to inaccurate permittivity estimates, leading to geometric distortions up to several meters. We present a novel inversion procedure to estimate volume parameters of ice sheets, namely, the depth of the scattering layer within the glacial volume and the dielectric permittivity of the ice, based on single-image single-polarization SAR acquisitions. The information is inherent in the processed SAR data as phase errors on the azimuth signals resulting from uncompensated non-linear propagation of the radar echoes through ice. We suggest a local map-drift autofocus approach to quantify and spatially resolve the phase errors and an inversion model to relate them to the penetration depth and permittivity. Testing the proposed technique using P-band SAR data acquired by DLR’s airborne sensor F-SAR during the ARCTIC15 campaign in Greenland shows promising results and good agreement with tomographic products of the analyzed test site.
Keywords: Ice; Permittivity; Synthetic aperture radar; Radar; Spaceborne radar; Scattering; Radar imaging; synthetic aperture radar (SAR); autofocus; tomography; cryosphere; glacier; penetration; depth

Automated Defect Detection for Non-Destructive Evaluation by Radar Imaging and Machine Learning - Ullmann, Ingrid; Egerer, Pascal; Schür, Jan; Vossiek, Martin (13th German Microwave Conference (GeMiC 2020), 2020)
This work provides a concept for a fully automated, non-invasive evaluation of dielectric objects by use of synthetic aperture radar (SAR) imaging combined with machine learning for application in non-destructive evaluation (NDE). For demonstration purposes we investigated a set of polyvinylchloride (PVC) test objects. A millimetre-wave imaging system is used to scan the objects. By employing subsurface SAR imaging techniques, high-resolution images from the objects’ insides can be obtained. These images are used as a dataset for a convolutional neural network. By training the network on several typical defect structures such as cracks, delaminations or contaminations, the proposed procedure enables an automated decision whether an object under test is intact or defective, independent of the kind of defec

Automated Synthesis of Shaped Beam Antenna Patterns with Implied Cross Coupling - Reck, C.; Berold, Ulrich; Schmidt, Lorenz-Peter (EuCAP, 2010)
In the following a numerical method to synthesize arbitrary antenna beamshapes of a phase and amplitude controlled array is described. A 25 year old method by Orchard, Elliot et al. is extended to include cross coupling between array elements as well as the single element characteristics. It is shown that the resulting beamshape provides a closer fitting to the desired beamshape function than the original approach at a reasonable computational burden.
lhft_intern.bib::Reck10

Automated threat detection and characterization with a polarimetric multistatic imaging system - Cenanovic, Amir; Gumbmann, Frank; Schmidt, Lorenz-Peter (EUSAR 2012, 2012)
In the field of security technology personnel screening systems are required, which provide detection and characterization of concealed items. This paper presents an approach for the detection and characterization of threats. It is based on the measurement with a polarimetric, multistatic imaging system, which operates in the frequency range of 75–95 GHz. Dielectric objects are identified and estimation of their material parameters is performed, by analyzing the co-polarization components of the polarimetric Sinclair matrix with the reflection ellipsometry method. The cross-polarization components of the scattering matrix are utilized, in order to implement an edge detection. The results show, that the analysis of the polarimetric imaging data represents a promising approach for an automated threat detection, without any invasion of personal privacy. Furthermore, it allows the estimation of the material parameters with a good accuracy.
lhft_intern.bib::Cenanovic2012

Automatic Detection of Concealed Dielectic Objects for Personnel Imaging - Ahmed, S. S.; Ostwald, O.; Schmidt, Lorenz-Peter (IEEE MTT-S International Microwave Workshop on Wireless Sensing, Local Positioning, and RFID (IMWS 2009 - Croatia), 2009)
A technique for the automatic detection of concealed dielectric objects carried by persons is presented. The method is applicable for microwave personnel scanners with sufficient signal bandwidth and is expected to resolve the trade-off with the privacy of the scanned persons, allowing for efficient detection without the need for a human operator. Algorithm description along with measurement results in W-band are presented.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.automa

Automatic Spatial Calibration of Near-Field MIMO Radar With Respect to Optical Depth Sensors - Wirth, Vanessa; Bräunig, Johanna; Khouri, Danti; Gutsche, Florian; Vossiek, Martin; Weyrich, Tim; Stamminger, Marc (IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2024)

Automatische Materialflussverfolgung auf Funkbasis (Automatic material flow monitoring based on wireless systems) - Miesen, Robert; Wittwer, Joachim; Vossiek, Martin (Stahl und Eisen, 2011)
lhft_intern.bib::Miesen2011

Automatischer Abgleich von Leistungskopplern - Helmreich, Klaus; Uygur, Gürkan (Tagungsband, 2008)
HF-Leistungskoppler, wie sie z.B. zur Kopplung mehrerer Sendermodule in DVB-T-Fernsehsendeanlagen zum Einsatz kommen, erfüllen aufgrund unvermeidbarer Fertigungstoleranzen zunächst nicht die hohen Anforderungen, die an ihre HF-Eigenschaften gestellt werden. Durch manuelles Verstellen von mehreren zu diesem Zweck am Koppler angebrachten Abgleichelementen müssen die HF-Eigenschaften soweit korrigiert werden, dass die Spezifikation erfüllt wird. In diesem Beitrag wird ein auf Optimierungsalgorithmen basierendes Verfahren vorgestellt, welches den automatischen Abgleich eines Kopplers ermöglicht. Ziel des Abgleichs ist eine Einstellung, bei der die Rückflussdämpfungen an den Sendereingängen sowohl im Normalbetrieb als auch in verschiedenen Störfällen (Ausfall einzelner Sendermodule) unter einem für die angeschlossenen Sendermodule unschädlichen Wert bleiben. Nur so ist ein zuverlässiger Betrieb von Sendeanlagen - auch in der Zeit vom Eintreten des Störfalls bis zu dessen Behebung - möglich.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.c3scha.automa

Automotive Radar Frequencies above 100 GHz and Their Advantages (W24) - Köhler, Mike; Schmidt, Lorenz-Peter (43th European Microwave Week, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.automo

Automotive Radar Operation Considerations and Concepts at Frequencies beyond 100 GHz - Köhler, Aaron; Hasch, J.; Gumbmann, Frank; Schmidt, Lorenz-Peter; Schür, Jan; Bloecher, H.-J. (Automative Radar Sensors in the 76-81 GHz Frequency Range, EuMW, 2010)
lhft_intern.bib::Koehler10a

Automotive Satellite Radar Sensor System based on an LTCC Miniature Frontend - Sickinger, Frank; Sturm, Christian; Vossiek, Martin; Janda, Libor; Stejskal, Ondrej (2018 IEEE MTT-S INTERNATIONAL CONFERENCE ON MICROWAVES FOR INTELLIGENT MOBILITY (ICMIM), 2018)
CRIS-Team WoS Importer:2019-06-04

A Vector Field Measurement System for 150 GHz - Weinzierl, Jochen; Schulz, Roland; Brand, Hans; Schmidt, Lorenz-Peter (25th International Conference on Infrared and Millimeter Waves, 2000)
The paper describes the design and realization of a heterodyne vector field measurement system. The system is designed to work in a frequency range from 148 GHz to 152 GHz with a dynamic range of about 75 dB and a phase uncertainty better than 3 degrees. It uses two channels for the measurement of the magnitude as well as the phase characteristics of an electromagnetic field. Two fundamental mixers at 150 GHz have been installed, which are both pumped by a 150 GHz phase locked solid-state oscillator unit. The system can be extended to the 300 GHz and 450 GHz frequency range by replacing these mixers by subharmonically pumped mixers. The mixers and two dielectric antennas, used as distortion minimized field probes, are mounted on a high precision 3D scanning platform. At the IF frequency of 160 MHz the vector analysis of the measured signals is done by an IF processing unit with considerably enhanced measurement accuracy by software corrections with a personal computer.
UnivIS-Import:2015-04-16:Pub.2000.tech.IE.LEH.avecto

Averaged large signal model of boost power factor corrector in boundary conduction mode - Schildbach, Christian; Kübrich, Daniel; Dürbaum, Thomas (2009 13th European Conference on Power Electronics and Applications, EPE '09, 2009)
Keywords: Measurement; Converter control; Power factor correction; Modeling; Simulation

Averaged large signal model of boost power factor corrector in boundary conduction mode - Schildbach, Christian; Kübrich, Daniel; Dürbaum, Thomas (EPE Power Electronics and Motion Control Conference, 2009)
A modeling approach of a power factor correction circuit operating in boundary conduction mode is presented. The PFC is controlled by a constant on-time of the switch. The effect of valley switching is simplified and taken into account as dead-time to generate a large signal model. On the basis a small signal model for the constant on-time controlled PFC voltage loop is derived. The large and small signal models are compared to measurements of the transfer function. For performing this low frequency transfer functions measurement a set-up using an oscilloscope and functional generator is described.
UnivIS-Import:2015-03-09:Pub.2009.tech.IE.lselek.averag
Keywords: Converter control; Measurement; Modeling; Power factor correction; Simulation

A versatile microwave plasma source and its application for a CO 2 laser - März, Martin; Oestreicher, Wolfgang (Review of Scientific Instruments, 1994)
A single ridged waveguide with nonconstant ridge height, operated with a traveling wave has been proven to be a versatile microwave plasma applicator. Easy dimensioning, inexpensive production, and compatibility to standard rectangular waveguide components are the main advantages compared to other designs. The described plasma source is especially suitable for any applications where an exceptionally uniform plasma is required. Design equations are given for easy adaption of the applicator to individual requirements. The applicator has been investigated for microwave excitation of a diffusion-cooled CO 2 laser. With a nonoptimized system, laser output power of 9 W could be achieved in a quasi-cw mode. A traveling discharge operating mode is described which is useful for plasma diagnostics and for pulsed laser applications.
Created from Fastlane, Scopus look-up

A Waveguide to Differential Stripline Transition for Planar mm Wave Antenna Measurements - Methfessel, Sebastian Dirk; Schmidt, Lorenz-Peter (Global Symposium on Millimeter Waves, GSMM, 2011)
lhft_intern.bib::Methfessel11

A Wireless Angle and Position Tracking Concept for Live Data Control of Advanced, Semi-Automated Manufacturing Processes - Lipka, Melanie; Meinel, David; Müller, Stefan; Sippel, Erik; Franke, Jörg; Vossiek, Martin (Sensors, 2020)
Despite recent industrial automation advances, small series production still requires a considerable amount of manual work, and training,and monitoring of workers is consuming a significant amount of time and manpower. Adopting live monitoring of the stages in manual production, along with the comprehensive representation of production steps, may help resolve this problem. For ergonomic live support, the overall system presented in this paper combines localization, torque control, and a rotation counter in a novel approach to monitor of semi-automated manufacturing processes. A major challenge in this context is tracking, especially hand-guided tools, without the disruptions and restrictions necessary with rigid position encoders. In this paper, a promising measurement concept involving wireless wave-based sensors for close-range position tracking in industrial surroundings is proposed. By using simple beacons, the major share of processing is transferred to fixed nodes, allowing for reduced hardware size and power consumption for the wireless mobile units. This requires designated localization approaches relying on only relative phase information, similar to the proposed Kalman-filter-based-beam-tracking approach. Measurement results show a beam-tracking accuracy of about 0.58 ∘" role="presentation">∘ in azimuth and 0.89 ∘" role="presentation">∘ in elevation, resulting in an overall tracking accuracy of about 3.18 cm.
Keywords: industrial automation; worker information system; localization; FMCW; angle-of-arrival

A wireless crane to vessel locating system for sea swell compensation - Nikolaiev, Anton; Kirsch, Fabian; Vossiek, Martin; Shu, Xinyu; Bohn, Christian; Duden, Heinrich (2014 20th International Conference on Microwaves, Radar and Wireless Communications, MIKON 2014, 2014)
Sea swell causes significant risk in transferring people and material to offshore constructions and oftentimes hamper the accessibility completely. The weather window where a construction is accessible can be enlarged notably if a crane is equipped with a sea swell compensation system. For a crane to vessel swell compensation system it is required to measure the 3D position of the crane load handling device relative to the deck of ship precisely, reliably and in real-time. In this paper a novel wireless crane to vessel locating system is introduced. Several secondary radar units that are mounted on the ship deck are measuring the distance to a responder unit attached to the crane boom. The 3D localization is based on a fusion of secondary radar distance measurements and the data from an inertial sensor platform. The fusion is done by a quaternion based extended Kalman filter which implements both multilateration and strapdown inertial navigation techniques. Real measurement data acquired with the inertial platform on a ship and radar data measured with the realized local positioning radar onshore are fed in a PC based simulation of the complete system. The real data simulations prove that the developed real time locating system provides the required position information precisely and reliably. By this it is shown that the novel wireless locating system is well suited for sea swell compensation equipment.
Keywords: inertial navigation; Kalman filter; Radar position measurement; radio navigation; swell compensation

A Wireless Joint Communication and Localization EMG-Sensing Concept for Movement Disorder Assessment - Brückner, Stefan; Weber, Jasmin; Michler, Fabian; Shanin, Nikita; Schober, Robert; Hagelauer, Amelie; Weigel, Robert; Gaßner, Heiko; Winkler, Jürgen; Eskofier, Björn; Vossiek, Martin (IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology, 2023)
Real-time sensory recording of the musculoskeletal system function is an important tool for the diagnosis, treatment planning, and optimal treatment execution of diseases, such as Parkinson's disease and osteoarthritis. This article presents a new wireless joint communication and localization electromyography (EMG)-sensing concept. An on-body sensor beacon measures EMG signals and wirelessly transmits them. At the same time, the spatial position and movement of the beacon is determined with high precision in real time using these transmitted radio signals. The seamless integration of multiple sensors avoids the need to synchronize and individually set up multiple independently operating sensors. An outstanding feature of the radio localization approach is that it does not require proprietary ultra-wideband signals or complicated time synchronization protocols, allowing for small and energy-efficient implementation. To demonstrate this novel concept, a wireless 3D-localizable EMG sensor was developed and experimentally evaluated. This new type of sensing concept allows, for the first time, the time-synchronous measurement of muscle activity and the underlying movement of the associated body part. URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10286030&isnumber=8000303<br
Keywords: Array signal processing; EMG; localization; radar tracking; radio communication

A Wireless Local Positioning System Concept and 6D Localization Approach for Cooperative Robot Swarms Based on Distance and Angle Measurements - Geiß, Johanna; Sippel, Erik; Gröschel, Patrick; Hehn, Markus; Schütz, Martin; Vossiek, Martin (IEEE Access, 2020)
In wireless sensor networks, spatially distributed nodes provide location-dependent sensorinformation. Therefore, knowledge about the 3D position of all nodes is crucial for the numerous appli-cations that require autonomous mobility. Furthermore, to acquire the nodes’ poses and the complete 6Dnetwork constellation, the 3D orientation of each node is also required. While many theoretical localiza-tion concepts exist for wireless sensor networks, there is still a lack of reliable system and localizationconcepts which enable robust real-time tracking in real-world scenarios. Therefore, we present a systemapproach based on an advanced 24 GHz wireless local positioning system, providing distance and anglemeasurements between pairs of nodes. Furthermore, an extended Kalman filter based localization algorithmis proposed, which evaluates these measurements to track the time varying 6D poses of all nodes inthe network. Because only relative measurements are available, one node is chosen to define a jointnavigation system. Hence, the proposed system works without any previously installed infrastructure orprior information of the network. The system and localization algorithm are validated by measurementsperformed in a mobile wireless sensor network comprising six nodes in an indoor scenario with strongmultipath propagation. However, despite the challenging environment, the system allows for a stable andaccurate 6D pose estimation of all robots in the network with 3D positioning root mean square errorsof 6 to 15 c

A Wireless Location System for Sensing the Relative Position between Mining Vehicles - Khrebtov, Pavel; Pöttker, Alois; Max, Stephan; Vossiek, Martin (2007 IEEE Instrumentation and Measurement Technology Conference, 2007)
In this paper a novel system and concept for sensing the relative position between mining vehicles is introduced. The localization is based on secondary radar like distance measurements between radar basestations on the excavator and transponders on the truck. Based on a novel geometry-matching algorithm it is possible to determine the relative position between truck and excavator precisely even in complex measurement and environmental conditions. The geometry-matching algorithm overcomes problems of usual triangulation based approaches because it efficiently reduces the risk to get an underdetermined set of geometric equations in conditions where measuring paths are shadowed or disturbed. The proposed concept allows for a steady and flexible control of all movements of the truck relative to an excavator and thus can contribute effectively to increase automation and productivity in future mining systems. The results of first full-scale experiments show the consistency and good performance of the proposed approach. © 2007 IEEE.
UnivIS-Import:2015-04-16:Pub.2007.tech.IE.LEH.awirel
Keywords: Automation; Local positioning; Mining vehicle location monitoring; Secondary radar

A Wireless Sensor for Ingot Mold Temperature Monitoring - Mamaschew, Sergej; Huellen, Ina; Schlueter, Jochen; Vossiek, Martin (SENSOR+TEST Conference 2011, 2011)
lhft_intern.bib::Mamaschew2011

Bandpass Filter with Tuneable Bandwidth and Center Frequency basedon Varactor Diodes - Reck, C; Trommer, Ralph; Schmidt, Lorenz-Peter (6th German Microwave Conference, 2011)
lhft_intern.bib::Reck2011a

Bandwidth Dependence of CW Ranging to UHF RFID Tags in Severe Multipath Environments - Li, Gang; Arnitz, Daniel; Ebelt, Randolf; Muehlmann, Ulrich; Witrisal, Klaus; Vossiek, Martin (5th Annual IEEE International Conference on RFID (IEEE RFID 2011), 2011)
lhft_intern.bib::Li2011a

Basics of Wireless Local Positioning - Vossiek, Martin; Ebelt, Randolf (IEEE IMS Workshop on Innovative and Highly Accurate Local Positioning Systems, IEEE International Microwave Symposium 2011 (IMS2011), 2011)
lhft_intern.bib::Vossiek2011

Beam Position and Energy Monitoring in Compact Linear Accelerators for Radiotherapy - Ruf, Marcel; Mueller, Sven; Setzer, Stefan; Schmidt, Lorenz-Peter (IEEE Transactions on Biomedical Engineering, 2014)
The experimental verification of a novel sensor topology capable of measuring both the position and energy of an electron beam inside a compact electron linear accelerator for radiotherapy is presented. The method applies microwave sensing techniques and allows for the noninterceptive monitoring of the respective beam parameters within compact accelerators for medical or industrial purposes. A state space feedback approach is described with the help of which beam displacements, once detected, can be corrected within a few system macropulses. The proof-of-principle experiments have been conducted with a prototype accelerator and customized hardware. Additionally, closed-loop operation with high accuracy is demonstrated. © 2013 IEE
UnivIS-Import:2015-03-09:Pub.2014.tech.IE.LEH.beampo
Keywords: Beam diagnostics; capacitive sensors; electron accelerators; linear accelerators; microwave sensors; state feedback

Beam Position Monitoring Based on Higher Beam Harmonics for Application in Compact Medical and Industrial Linear Electron Accelerators - Ruf, Marcel; Schmidt, Lorenz-Peter; Setzer, S. (1st International Particle Accelerator Conference, IPAC10, 2010)
lhft_intern.bib::Ruf10a

Beam Position Monitoring based on RF Heterodyning and Log-Ratio Signal Processing for Electron Accelerator Systems - Ruf, Marcel; Schmidt, Lorenz-Peter; Setzer, S. (41st European Microwave Conference, 2011)
(BPM) and control is presented. For the first time, the combination of conventional BPM hardware and individually designed RF circuitry for S-Band accelerators is investigated and its applicability to beam position measurements is validated. The concept is based on heterodyning higher harmonics of the beam spectrum and processing them by means of the log- ratio technique. Measurement results gathered with an 8-channel receiver module and a test stand, based on a 6 MeV electron beam, are also presented.
lhft_intern.bib::Ruf11a

Beam Position Monitoring in Electron Accelerators - Ruf, Marcel; Martius, Siegfried; Setzer, St.; Mueller, S. (Frequenz, 2009)
UnivIS-Import:2015-03-09:Pub.2009.tech.IE.LEH.beampo

Berechnung der Leitungsparameter quasiplanarer Wellenleiter fuer integrierteMillimeterwellen-Schaltungen - Schmidt, Lorenz-Peter; Menzel, W (Wissenschaftliche Berichte AEG Telefunken, 1981)
lhft_intern.bib::Schmidt7

Best Practice Guide for Planar S-Parameter Measurements using Vector Network Analysers : EMPIR - 14IND02 PlanarCal - Arz, Uwe; Probst, Thorsten; Kuhlmann, Karsten; Ridler, Nick; Shang, Xiaobang; Mubarak, Faisal; Hoffmann, Johannes; Wollensack, Michael; Zeier, Markus; Phung, Gia Ngoc; Heinrich, Wolfgang; Lomakin, Konstantin; et al. (2019)
In the European project PlanarCal a major effort has been undertaken to characterise components and devices for eventual use in high-speed and microwave applications (e.g. wireless communications, automotive radar and medical sensing) with known measurement uncertainties. It is the purpose of this Best Practice Guide to give an overview of the major outcomes of this project together with useful information on recommended measurement practice, different sources of uncertainty and the determination of uncertainties. This Best Practice Guide is not intended to replace available literature which offers comprehensive introductions to the subject of on-wafer measurements and deembedding. Instead, this Guide aims to present useful best practice recommendations together with key takeaways developed from the research performed in PlanarCal during the project’s lifetime from 2015 until 201
Keywords: Calibration; on-wafer; S-parameters; traceability; uncertainty budget; coplanar waveguide (CPW); electromagnetic ﬁeld simulation; parasitic modes; substrate modes; multiline-thru-reﬂect-line (mTRL); microwave probes; extreme impedance measurement; impedance mismatch; microwave interferometry; nanoelectronics; nanostructures; noise; vector network analyzer (VNA)

Beyond 1 Gbit/s Transmission over 1 mm Diameter Plastic Optical Fiber employing DMT for In-Home Communication Systems - Visani, Davide; Okonkwo, Chigo; Loquai, Sven; Yang, Hejie; Shi, Yan; Van Den Boom, Henrie; Ditewig, Ton; Tartarini, Giovanni; Schmauß, Bernhard; Lee, Jeffrey; Koonen, Ton; Tangdiongga, Eduward (Journal of Lightwave Technology, 2011)
lhft_intern.bib::Visani11

Birefringence in Injection-Molded Cyclic Olefin Copolymer Substrates and Its Impact on Integrated Photonic Structures - Kefer, Stefan; Limbach, Tobias; Pape, Natalie; Klamt, Kathrin; Schmauß, Bernhard; Hellmann, Ralf (Polymers, 2024)
This contribution quantifies the birefringence within injection-molded cyclic olefin copolymer plates and discusses its impact on the mechanical properties of the plates. It also focuses on the impact of birefringence on integrated waveguides and Bragg gratings and provides fabrication guidelines for such structures. The anisotropy in all three dimensions of the workpiece is examined by means of polarimetry and a prism coupler. It is found that the birefringence is inhomogenously distributed within the workpieces, whereas the maximum birefringence not only varies locally, but also depends on the observation direction. Overall, a maximum birefringence of 10 × 10−4 is found at the plate’s surface near the injection gate. The anisotropy then reduces exponentially towards the center of the workpiece and saturates at 1.8 × 10−4, in a depth of 0.4 mm. Thus, the birefringence strongly affects near-surface photonic structures. It is found that, depending on their orientation and the local birefringence of the substrate, waveguides and Bragg gratings fabricated with comparable parameters behave completely differently in terms of polarization-dependent optical attenuation, cross-sectional intensity distribution and Bragg reflection signal. For example, the support of the TM mode can vary between total loss and an optical attenuation of 0.9 dB × cm−1. In consequence, this study underlines the importance of quantifying the birefringent state of an injection-molded cyclic olefin copolymer workpiece if it is supposed to serve as a substrate for integrated photonic structures. The study furthermore demonstrates that birefringence effects can be omitted by burying the photonic structures deeper into the volume of the thermoplastic.
CRIS-Team Scopus Importer:2024-02-02
Keywords: birefringence; Bragg grating; cyclic olefin copolymer; injection molding; integrated photonics

Body Scanner Using Active Imaging - Adametz, Julian; Schmidt, Lorenz-Peter (IMS 2013 Workshop on Microwave Systems for Security Applications, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.bodysc

Breitbandige Finleitungs-Richtkoppler - Callsen, H; Schmidt, Lorenz-Peter; Solbach, K (Wissenschaftliche Berichte AEG Telefunken, 1981)
lhft_intern.bib::Schmidt8

Bridge the Gap between Simulation and Test: An OSA-Compliant Virtual Test Environment - Lu, Ping; Glaser, Daniel; Weichslgartner, Susanne; Uygur, Gürkan; Helmreich, Klaus; Lechner, Armin (Proceedings, 2009)
Virtual Test (VT) is a promising technique that facilitates test development and cuts time-to-market especially for analog/mixed-signal/RF devices. While the concept has been around for more than a decade and its benefits are widely acknowledged, to date it has not become a standard technique in the day-to-day business of test development. The major difficulties are: weak integration between test environment and simulation environment, lack of flexible and sophisticated simulation library for test resource and insufficient simulation efficiency. The paper discusses solutions for addressing the gaps and presents a platform independent - yet easy integrateable Virtual Test Environment (VTE). It is achieved by following steps: first, OSA-compliance - using industry standards with wide acceptance including data format, service API and protocols to pave the way for easy integration. Second, achieving interaction with the test program by modeling test resources with software control interface, this allows simulation models to be dynamically assembled together and exchanging information with the test program during run-time. At last, modeling optimization - the models of test resources in our VTE have different abstraction levels supporting both static and dynamic assembly during dynamic test program execution. Analysis is performed with respect to accuracy vs. efficiency during model assembling phase to cut computational burden. In the end, a seamless integration of VT approach into test development flow is explained. ©2009 IEEE.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.c3scha.bridge

Broadband beamforming and null-steering based on fractional delay in OFDM systems - Martinez Garcia, Javier; Zarzuelo, C; Iglesias, V; Grajal, J (20th European Wireless Conference, 2014)
lhft_intern.bib::Martinez14

Broadband Detector Array Concept for 3D Holographic Imaging at THz Frequencies - Schildbach, Christian; Schür, Jan; Schmidt, Lorenz-Peter (43th European Microwave Week, 2013)
A field coupled detector is presented including planar antenna design as well as the video amplifier topology. The compact antenna design is suitable for application in dense antenna arrays. Particularly an array concept is shown that suits for holographic imaging at frequencies beyond 200 GHz. For this purpose a broadband planar antenna is designed for frequencies from 230 GHz to 325 GHz, allowing for high depth resolution in an imaging system. Optimization methods utilized to improve the antenna perfomance are discussed. The presented transimpedance amplifier design offers a low noise figure and a protection for the diode, as it regulates the diode voltage to zero. An optimal diode impedance for this amplifier topology is derived. Simulation and measurement results are presented. © 2013 European Microwave Association.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.broadb

Broadband Electrical Design and Modelling of Packages Integrated in LTCC-Substrate - Nisznansky, Martin; Ziegler, Christof; Schmidt, Lorenz-Peter; Hocke, Ralf; Wohlgemuth, O. (Proceedings of IMAPS Conference and Exhibition on Ceramic Interconnect Technology, 2003)
Substrate integrated package based on LTCC-technology with bandwidth of 50 GHz was designed. Full wave electromagnetic analysis of all included interconnects was performed and verified by measurement. Our work is especially focused on novel interconnects like flip-chip and differential transmission lines which enable an increase of bandwidth of the components. For the design of high speed SiGe-chips which will be embedded in LTCC-packages and modules it is interesting to know the influence of wire-bonds and flip-chip interconnects on module performance. Therefore equivalent circuit models were developed for these two typical structures that can be used in chip design tools like CADENCE. The behavior of interconnects were investigated not only in frequency domain but in time domain as well. As digital signals are processed an estimation of their distortion in the time domain is needed. Hence eye-diagrams were calculated from simulated data. Important digital signal characteristics like eye-opening and jitter can be estimated from this diagram. From the presented results we can see that the designed interconnects for LTCC-packages fulfill the requirements on bandwidth and minimize signal distortion.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.broadb
Keywords: Circuit model; Coupled lines; Differential excitation; Flip-chip; High speed interconnects; Wire-bond

Broadband Low-Loss Fan-In Chip-to-Package Interconnect Enabling System-in-Package Applications Beyond 220 GHz - Pfahler, Tim; Breun, Sascha; Engel, Lukas; Geissler, Christian; Schür, Jan; Vossiek, Martin (IEEE Transactions on Components, Packaging and Manufacturing Technology, 2024)
This paper presents a broadband low-loss fan-in wafer level ball grid array (WLB) vertical through-mold-via (TMV) interconnect that enables highly integrated system-in-package (SiP) applications beyond 220 GHz. The dedicate advantage of the proposed approach is to further minimize the separation between package components (e.g., antenna in package (AiP)) and on-chip receiver or transmitter chain. To demonstrate the robustness of the TMV interconnect design, the necessity for co-simulation of the integrated circuit (IC) package and the IC itself during the package-design is shown. Therefore, an in-depth analysis of the suppression of parasitic mode oscillation inside silicon is carried out. Furthermore, the parasitic radiation loss at the TMV interconnect discontinuity is given and a verification of the proposed TMV due to high agreement of simulation and measurement results is demonstrated. The interconnect has been verified with a measured 10 dB return loss bandwidth of 38 GHz and a de-embedded insertion loss of less than 2.8 dB at 275 GHz, which enables a compact low-loss broadband signal transition from active IC components in the backend-of-line (BEOL) to passive components in package. Compared to fan-out WLB, the developed fan-in WLB solution enables higher integration density of active and passive components with the shortest interconnects for minimal insertion loss. Thus, the proposed fan-in TMV packaging provides a very compact, easy-to-assemble and cost-efficient alternative for SiP designs for future broadband communication and sensing solutions.<br
CRIS-Team Scopus Importer:2024-04-19
Keywords: Packaging; Antennas; Assembly; Integrated circuit interconnections; Copper; Broadband communication; Bandwidth; Assembly; fan-in WLB (wafer level ball grid array); fan-out WLB; heterogeneous system design; interconnect; signal transition characterization; system-in-package (SiP); wafer level packaging

Broadband millimetre-wave PIN-diode attenuator with double-ridge waveguide flanges - Schmidt, Lorenz-Peter; Meinel, H (Electronics Letters, 1982)
lhft_intern.bib::Schmidt11

Broadband MIMO Testbed for the Development and Research on 6G - Nuß, Benjamin; Gröschel, Patrick; Pfau, Johannes; Becker, Jürgen; Vossiek, Martin; Zwick, Thomas (European Wireless 2022; 27th European Wireless Conference, 2022)

Broadband, nonuniform stripline directional couplers for use in VNA testsets - Hrobak, M.; Sterns, M.; Seler, E.; Schrauder, T.; Schramm, M.; Schmidt, Lorenz-Peter (7th German Microwave Conference (GeMiC2012), 2012)
Scattering parameter testsets of vector network analyzer (VNA) base instruments require backward wave directional couplers with sufficiently high directivity. This paper describes a synthesis procedure of symmetric, nonuniform couplers based on common multilayer printed circuit board (PCB) technology. The utilized offset coupled striplines (STL) are characterized by 2D electromagnetic (EM) field simulations in the frequency domain. Two loose directional couplers with directivity values greater than 15 dB from 0.003 MHz to 40 GHz resp. 29 GHz and greater than 5 dB up to 50 GHz resp. 70 GHz are proposed. The necessity of well matched transitions from STL to microstrip line (MSL) is outlined and two possible realizations are discussed. Measurement data of the manufactured couplers is presented, the arising deviations are clearly mapped to specific manufacturing tolerances. The minimum requirements for the applied PCB technology that guarantee successful designs are highlighted.
lhft_intern.bib::hrobakGemicCoup

Broadband Planar Ring Mixers with DGS-Marchand Baluns in the Millimeter Wave Frequency Range - Rehner, Robert; Schneiderbanger, Dirk; Sterns, Michael; Martius, Siegfried; Schmidt, Lorenz-Peter (GEMIC March 2008, 2008)
Planar hybrid ring mixers in the millimeter wave range for frequencies up to 80 GHz are presented. They exhibit conversion losses lower than 15 dB up to frequencies higher than 70 GHz, with a very wide IF-bandwidth range from DC up to 22 GHz. The balancing of the input signals is realized by using broadband DGS-Marchand baluns, thus enabling an operation bandwidth of the mixers of more than 80%. The very high couplings at the baluns are realized by applying defected ground structures to the backside metallization of the circuits. The mixer circuits can be easily integrated into larger circuits. The design and the measurement results for three different mixer realizations are presented and compared.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.broadb

Broadband polarimetric mmWave antennas with differential stripline feed - Thurn, Karsten; Methfessel, Sebastian Dirk; Schmidt, Lorenz-Peter (European Conference on Antennas and Propagation, 2012)
Two approaches for differentially fed, polarimetric antennas with a center frequency of 77.5 GHz are introduced. These are an aperture-coupled patch (ACP) antenna and a monopole antenna with two differentially fed monopole pairs. Easy planar integration with differential MMICs is given through the differential stripline feed. Both antennas are designed for high bandwidth from 70 to 85 GHz for 10 dB return loss and high polarization purity. A stacked conical horn included in both designs results in a high gain of 8.5 dBi and a radiation pattern with one symmetric main beam without significant side lobes, reducing coupling to other elements in a future antenna array. After an introduction, design goals for the antennas are presented. Then, the design procedures for the two concepts are described together with simulation results. For measurement of the antennas, a feed network has been developed and the monopole antenna has been chosen for realization. The paper will be concluded by measurement results that are in good agreement with the simulations.
lhft_intern.bib::Thurn2012

Broadband, Spectrally Conrolled raman-active Attenuator - Holtmannspötter, Michael; Pitschujew, E.; Schmauß, Bernhard (The European Conference on Optical Communication 2009 (ECOC 2009), Wien, September, 2009)
We present numerical investigations on a broadband Raman-active attenuator using a WDM-scheme of control signals. It is shown to hold a feasible control characteristic for mitigation of residual transients arising in spite of inline-amplifier control.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.broadb

Broadband time-domain absorption spectroscopy with a ns-pulse supercontinuum source - Sych, Y.; Engelbrecht, Rainer; Schmauß, Bernhard; Kozlov, D.; Seeger, T.; Leipertz, A. (Optics Express, 2010)
lhft_intern.bib::Sych10

Burn wound assessment through microwave imaging - Oppelt, Daniel; Vossiek, Martin (IMS 2018 Workshop on Microwave to THz imaging technologies for biomedical applications, 2018)

Calculation of Raman Fiber Laser Spectra by a Combination of Shooting Method and Split-Step Fourier Transform Algorithm - Hagen, J.; Engelbrecht, Rainer; Wetzel, O.; Siekiera, Alexander; Schmauß, Bernhard (ECOC September, 2007)
A numerical method for calculation of FWM spectral broadening in Raman fiber lasers is presented. It is based on the steady-state equations and the nonlinear Schrdinger equation. Numerical results are confirmed by measurements.
UnivIS-Import:2015-04-16:Pub.2007.tech.IE.LEH.calcul

Calibrating visual sensors and actuators in distributed platforms - Hörster, Eva; Lienhart, R.; Kellermann, Walter; Bouguet, J. Y. (Computer Vision for Interactive and Intelligent Environments 2005, 2005)
Many novel multimedia, home entertainment, visual surveillance and health applications use multiple audio-visual sensors and actuators. In this paper we present a novel approach for position and pose calibration of visual sensors and actuators, i.e. cameras and displays, in a distributed network of general purpose computing devices. It complements our work on position calibration of audio sensors and actuators in a distributed computing platform [14]. The approach is suitable for a wide range of possible - even mobile - setups since (a) synchronization is not required, (b) it works automatically, (c) only weak restrictions are imposed on the positions of the cameras and displays, and (d) no upper limit on the number of cameras and displays under calibration is imposed. Corresponding points across different camera images are established automatically and found with subpixel accuracy. Cameras do not have to share one common view. Only a reasonable overlap between camera subgroups is necessary. The method has been sucessfully tested in numerous multi-camera environments with a varying number of cameras and displays and has proven itself to work extremely accurate. © 2005 IEE

Calibration of electromagnetic field simulations of MR coil arraysfor accurate quantitative comparison with the measured image SNR - Stumpf, C.; Rehner, R.; Martius, Siegfried; Vester, M.; Engelbrecht, Rainer; Schmidt, Lorenz-Peter (Intl. Soc. Mag. Reson. Med. 20th, 2012)
lhft_intern.bib::Stumpf2012

Calibration of MIMO Fully Polarimetric Imaging Radar Systems with Passive Targets - Körner, Georg; Oppelt, Daniel; Adametz, Julian; Vossiek, Martin (Frequenz, 2019)
The performance of polarimetric imaging radar systems depends greatly on how well they are calibrated. The complexity of the calibration procedure scales with the number of send and receive antennas, i. e. the size of the antenna array. This article proposes a practical and effective approach for calibrating a polarimetric near field MIMO imaging radar using only two simple passive targets. The calibration requires four measurement steps: An empty space measurement for suppressing direct mutual coupling between the channels. An offset short calibration with the specular reflection of a planar metal plate for the co-polarized channels. Two measurements with a dihedral reflector inclined at different angles for the cross-polarized calibratio
Keywords: radar calibration; multistatic radar; MIMO radar; synthetic aperture radar; millimeter-wave radar

Calibration of visual sensors and actuators in distributed computing platforms - Hörster, Eva; Lienhart, R.; Kellermann, Walter; Bouguet, J. Y. (3rd ACM International Workshop on Video Surveillance and Sensor Networks, VSSN 2005, 2005)
Many novel multimedia and visual surveillance applications use multiple sensors and actuators. We present a novel approach for position calibration of visual sensors and actuators, i.e. cameras and displays, in a distributed network of general purpose computing devices. The proposed approach is very suitable for calibration in a wide range of setups since (a) synchronization is not required, (b) it works fully automatic, (c) only weak restrictions are imposed on the positions of the cameras and displays, and (d) no upper limit on the number of cameras and displays under calibration is imposed. Corresponding points across different camera images are established automatically and found with subpixel accuracy. Cameras do not have to share one common view, only a reasonable overlap between camera subgroups is necessary. The method has been sucessfully tested in numerous multi-camera environments with a varying number of cameras and displays. It has proven itself to work extremely accurate. Performance results are reporte
Keywords: Multi-camera calibration; Position calibration; Sensor networks

Capacity and outage of multimode fiber with statistical bends - Buelow, H.; Al Hashimi, Hussein Husham Jasim; Abebe, Birhanu Tamene; Schmauß, Bernhard (Optical Fiber Communication 2012, 2012)
Information capacity of a group delay spread minimized MMF carrying 15 spatial modes is calculated taking into account limited inter mode group coupling of statistical fiber bends and their attenuation of higher order modes.
lhft_intern.bib::Buelow2012

Capacity of the Gaussian Two-Hop Full-Duplex Relay Channel With Residual Self-Interference - Zlatanov, Nikola; Sippel, Erik; Jamali Kooshkghazi, Vahid; Schober, Robert (IEEE Transactions on Communications, 2017)
In this paper, we investigate the capacity of the Gaussian two-hop full-duplex (FD) relay channel with residual self-interference. This channel is comprised of a source, an FD relay, and a destination, where a direct source-destination link does not exist and the FD relay is impaired by residual self-interference. We adopt the worst case linear self-interference model with respect to the channel capacity, and model the residual self-interference as a Gaussian random variable whose variance depends on the amplitude of the transmit symbol of the relay. For this channel, we derive the capacity and propose an explicit capacity-achieving coding scheme. Thereby, we show that the optimal input distribution at the source is Gaussian and its variance depends on the amplitude of the transmit symbol of the relay. On the other hand, the optimal input distribution at the relay is discrete or Gaussian, where the latter case occurs only when the relay-destination link is the bottleneck link. The derived capacity converges to the capacity of the two-hop ideal FD relay channel without self-interference and to the capacity of the two-hop half-duplex (HD) relay channel in the limiting cases when the residual self-interference is zero and infinite, respectively. Our numerical results show that significant performance gains are achieved with the proposed capacity-achieving coding scheme compared with the achievable rates of conventional HD relaying and/or conventional FD relaying.

Capacity of the Gaussian Two-Hop Full-Duplex Relay Channel with Self-Interference - Zlatanov, Nikola; Sippel, Erik; Jamali, Vahid; Schober, Robert (2016 IEEE Global Communications Conference (GLOBECOM), 2016)
In this paper, we investigate the capacity of the Gaussian two-hop full-duplex (FD) relay channel with self-interference. This channel is comprised of a source, an FD relay, and a destination, where a direct source-destination link does not exist and the FD relay is impaired by self- interference. We model the self-interference as an additive Gaussian random variable whose variance is proportional to the amplitude of the transmit symbol at the relay. For this channel, we derive the capacity and propose an explicit capacity- achieving coding scheme. Thereby, we show that the optimal input distribution at the source is Gaussian and its variance depends on the amplitude of the transmit symbol at the relay. On the other hand, the optimal input distribution at the relay is discrete or Gaussian, where the latter case occurs only when the relay- destination link is the bottleneck link. The derived capacity converges to the capacity of the two-hop ideal FD relay channel without self- interference and to the capacity of the two-hop half-duplex (HD) relay channel in the limiting cases when the self-interference is zero and infinite, respectively. Our numerical results show that significant performance gains are achieved using the proposed capacity-achieving coding scheme compared to the achievable rates of conventional FD relaying and HD relayin
lhft_intern.bib::SipplE2016a

Carrier and Phase Recovery Algorithms for QAM Constellations: Real-time Implementations - Bisplinghoff, Andreas; Fludger, C.; Kupfer, T.; Schmauß, Bernhard (Signal Processing in Photonic Communications (SPPCom), 2013)
We compare carrier phase recovery algorithms with respect to performance and we discuss their feasibility for real-time implementation in coherent transceivers.
lhft_intern.bib::Bisplinghoff2013

Cascaded Phase-Preserving Amplitude Regeneration in a DPSK Transmission System - Schmauß, Bernhard; Stephan, Christian; Sponsel, Klaus; Onishchukov, Georgy; Leuchs, Gerd (ECOC 2009, Vienna, Austria, 20-24 September, 2009)
Experimental results obtained on 10 Gb/s RZ-DPSK transmission in a recirculating fiber-loop setup show that nonlinear amplifying loop mirrors can efficiently enhance system performance. Main limiting factor is amplified Rayleigh backscattering in highly nonlinear fiber. © VDE VERLAG GMBH.
UnivIS-Import:2017-12-18:Pub.2009.tech.IE.LEH.cascad

Cascaded phase-preserving multilevel amplitude regeneration - Röthlingshöfer, Tobias; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Optics Express, 2014)
The performance of cascaded in-line phase-preserving amplitude regeneration using nonlinear amplifying loop mirrors has been studied in numerical simulations. As an example of a spectrally efficient modulation format with two amplitude states and multiple phase states, the regeneration performance of a star-16QAM format, basically an 8PSK format with two amplitude levels, was evaluated. An increased robustness against amplified spontaneous emission and nonlinear phase noise was observed resulting in a significantly increased transmission distance.
lhft_intern.bib::Roethlingshoefer2014_4

Cavity Damping of a 2.5 THz Resonator System Using Electro-Optically Stimulated Silicon - Biber, Stephan; Schneiderbanger, Dirk; Schulz, R.; Schmidt, Lorenz-Peter (Proceedings of the 28th Int. Conference on Infrared and Milimeter Waves, Otsu, Japan, 2003)
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.cavity

Channel Parameter Estimation for Polarization Diverse Coherent Receivers - Geyer, J; Hauske, F; Fludger, C; Duthel, T; Kuschnerov, M; Piyawanno, K; van den Borne, D; Schmidt, E; Spinnler, B; de Waardt, H; Lankl, B; Schmauß, Bernhard (IEEE Photonics Technology Letters, 2008)
A robust in-service estimation of fiber channel parameters from equalizer parameters of a polarization diverse coherent receiver is presented. The equations used for estimation are evolved from a theoretical fiber channel model. The theory is validated based on simulations and data from transmission experiment
lhft_intern.bib::geyer08

Characterisation of an RZ-DQPSK transmitter using coherent detection - Schmauß, Bernhard; Fludger, C.R.S.; Voß, Axel; Duthel, T.; Schulien, C. (ECOC September, 2007)
We characterise the optical field from an RZ-DQPSK transmitter using coherently detected constellation diagrams. We show the dependence on bias and phase offsets, as well as timing mismatch.
UnivIS-Import:2015-04-16:Pub.2007.tech.IE.LEH.charac

Characteristics of a generalized fin-line for millimeter wave integrated circuits - Schmidt, Lorenz-Peter; Itoh, T (International Journal of Infrared and Millimeter Waves, 1981)
Generalized fin-lines are analyzed which consist of slots located on more than one interface between dielectric layers inserted in parallel with the E-plane of a waveguide. The analysis is based on a simplified formulation technique based on the spectral domain immittance matrix followed by a Galerkin's method. It allows as many slots as one desires at each interface, and the locations and the widths of these slots are arbitrary. The numerical process to carry out the present analysis is rather efficient. Some numerical data, including propagation constants of the propagating modes as well as characteristic impedances are presented for several structures considered useful for millimeter-wave circuit application
lhft_intern.bib::Schmidt5

Characteristics of Anisotropic Conducting Polymers Suggest Feasibility of Test Fixtures up to 110 GHz - Sippel, Mark; Lomakin, Konstantin; Gold, Gerald; Helmreich, Klaus (Electronics, 2017)
Applications and volume of integrated circuits operating at frequencies up to 100 GHz are steadily increasing. This establishes serious challenges, especially for temporarily contacting such products during manufacturing tests with appropriate signal integrity. At present, existing test socket concepts have reached their applicability limit. The most promising candidates to meet the requirements of future microwave device interfacing are thin, anisotropic conducting polymers. This paper reports a survey covering measurement methodology for signal integrity properties of conducting polymers, model parameter extraction, measurement results from various materials, reliability issues, and a prototype application. View Full-Text</

Characteristics of Unilateral Fin-Line Structures with Arbitrarily Located Slots - Schmidt, Lorenz-Peter; Itoh, T; Hofmann, H (MTT-Symposium and IEEE Trans. MTT-29, 1980)
Generalized unilateral fin-line configurations for extended mm-wave applications are analyzed using the equivalent transmission line concept in the spectral domain. Numerical results for the frequency dependent propagation constants and characteristic impedances of various structures are presente
lhft_intern.bib::Schmidt6

Characterization of a narrowband Raman MOPA with short master oscillator - Siekiera, Alexander; Engelbrecht, Rainer; Nothofer, Andreas; Schmauß, Bernhard (SPIE 8237 Photonics West, 2012)
Raman fiber lasers (RFL) with a narrow spectral bandwidth are important light sources, e.g. for applications that require second-harmonic generation. Non-linear optical processes within the fiber like four-wave mixing (FWM) lead to spectral broadening, due to the generation of frequency components outside of the initial laser bandwidth. This mainly results from FWM of the longitudinal modes generated in the laser cavity. Consequently a reduced number of modes with increased frequency spacing, which is obtained by using a short laser cavity, is expected to reduce the spectral broadening. We investigate a Raman master oscillator power amplifier (MOPA) configuration, consisting of a RFL with a very short cavity length of 17 cm and a subsequent Raman amplifier of 55 m length. Pumping with 8 W power of an Ytterbium-doped fiber laser at 1100 nm, the Stokes wave at 1151 nm is generated, yielding 0.7 W Stokes power with a narrow full-width at half-maximum bandwidth of 60 pm at the MO output. From the measured frequency spacing of 607 MHz between the longitudinal modes a maximum number of 24 modes can be calculated to oscillate within the bandwidth of the MO output. The residual pump power is used to amplify the Stokes wave in a subsequent Raman amplifier. At the MOPA output the amplified Stokes power is 4.3 W with a strongly broadened bandwidth of 328 pm. Thus our results show that even for a Stokes wave with only few longitudinal modes at the MO output, strong FWM induced spectral broadening occurs within the amplifie
lhft_intern.bib::Siekiera2012

Characterization of Micromachined Waveguide Hybrids at 350 and 650 GHz - Biber, Stephan; Murk, A.; Tils, T.; Pütz, P.; Schmidt, Lorenz-Peter; Kämpfer, N. (17th International Symposium on Space THz Technology - ISSTT 2006, Paris, May, 2006)
We present measurement results of two different hybrid couplers at submillimeter wavelengths. The devices under test were a 650 GHz coupler, which has been micromachined in Silicon by deep reactive ion etching, and two versions of a 345 GHz coupler machined out of brass. In order to determine the amplitude and phase balance of the coupling section the differences between the connecting waveguides have to be taken into account. We corrected the measurements under the assumption that the coupling section itself is fully symmetrical, which results in a good matching between the measured and the simulated performance.
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.charac

Characterization of Multi-Core Fiber Group Delay with Correlation OTDR and Modulation Phase Shift Methods - Azendorfm, Florian; Dochhan, Annika; Wilczynski, Krzysztof; Szostkiewicz, Lukasz; Urban, Patryk; Schmauß, Bernhard; Vilchez, Francisco Javier; Nadal, Laia; Moreolo, Michela Svaluto; Fabrega, Josep M.; Eiselt, Michael (2020 Optical Fiber Communications Conference and Exhibition, OFC 2020 - Proceedings, 2020)
Using a Correlation-OTDR and a modulation phase shift method we characterized four multi-core fibers. The results show that the differential delay depends on the position of the core in the fiber and varies with temperature.
CRIS-Team Scopus Importer:2020-06-02

Characterization of NIR-Lasers for Diode Laser Spectroscopy - Buchtal, R.; Engelbrecht, Rainer; Tröllsch, A.; Zinn, P. (TDLS - 7th International Conference on Tuneable Diode Laser Spectroscopy, 13.-17.07.09, Zermatt, Schweiz, 2009)
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.charac

Characterization of Rotating Objects with Tomographic Reconstruction of Multi-Aspect Scattered Signals - Martinez Garcia, Javier; Thurn, Karsten; Vossiek, Martin (IEEE Transactions on Aerospace and Electronic Systems, 2019)
Abstract—The backscattered signals of objects underspinning motion or with rotating parts provide very richinformation that can be used for classification tasks,parameter extraction etc. Obtaining such informationfrom non-cooperative objects with an unknown targetaspect is often a complicated task with a monostaticconfiguration. A multistatic radar on the other hand, canexploit the spatial diversity to extract the informationfrom the time-frequency representations obtained frommultiple aspect-angles. In this work, we propose a tomo-graphic approach for characterizing spinning objects interms of their shape, size and rotation parameters usinga narrowband multistatic radar. A 2D image is recon-structed after a full rotation period using tomographicmethods that allows not only to estimate the shape ofthe target, but also the rotation parameters and thedimensions of the object. This is done very efficientlyby combining the tomographic images from differentaspect-angles on the transformed log-polar space, insteadof the time-frequency representations. Simulations andmeasurements were conducted for the proof of concept.The measurement results with a simple target and a CWK-Band radar show errors below 3◦for the orientationestimation and below 5% for the estimation of the object'sdiamete
Keywords: Tomography; Image reconstruction; Radar imaging; Doppler shift; Shape; Narrowband; Multistatic radar; narrowband radar; tomographic reconstruction; total rotation velocity estimation

Characterization of Short PM Raman Fiber Lasers with a Small Spectral Bandwidth - Engelbrecht, Rainer; Siekiera, A.; Bauer, R.; Neumann, R.; Schmauß, Bernhard (Optical Fiber Communication 2011, 2011)
lhft_intern.bib::Engelbrecht2011

Charakterisierung semirigider Koaxialantennen für die interstitielle und endokavitäre Mikrowellenhyperthermie. - Erb, J.; Klautke, G.; Seegenschmiedt, Heinrich; Engelbrecht, Rainer; Schaller, Gerhard; Sauer, R. (Strahlentherapie und Onkologie, 1994)
UnivIS-Import:2015-03-05:Pub.1994.tech.IE.LEH.charak

Charakterisierung und Qualitätssicherung von intersitiellen koaxialen Mikrowellen-Dipolantennen - Erb, J; Engelbrecht, Rainer; Schaller, G; Roos, D; Seegenschmiedt, H; Mueller, R; Sauer, R (1993)
lhft_intern.bib::thirty_years_LHFT_325

Charakterisierung und Qualitätssicherung von interstitiellen koaxialen Mikrowellen-Dipolantennen - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard; Roos, D.; Seegenschmiedt, Heinrich; Müller, R. G.; Sauer, R. (24. Wissenschaftliche Tagung der Deutschen Gesellschaft für Medizinische Physik (DGMP), 1993)
UnivIS-Import:2015-04-16:Pub.1993.tech.IE.LEH.charak

Charakterisierung und Qualitätssicherung von interstitiellen koaxialen Mikrowellen-Dipolantennen - Erb, J; Engelbrecht, Rainer; Schaller, G; Seegenschmiedt, H; Mueller, R; Sauer, R; Roos, D (1993)
lhft_intern.bib::thirty_years_LHFT_345

Chipless RFID Polarimetric Radar Barcodes Encoded by Dipole Scattering Domains - Stief, Patrick; Ullmann, Ingrid; Körner, Georg; Root, Konstantin; Vossiek, Martin (IEEE Journal of Microwaves, 2022)
Recently, a novel chipless radio-frequency identification (RFID) concept based on polarimetric radar barcodes was introduced. These tags are similar to the well known optical quick response codes (QR codes). In polarimetric radar barcodes the information is stored as polarimetrically coded areas arranged in a grid and read out by an imaging radar. This paper presents a novel concept for elegantly creating polarimetric barcodes based on dipole scattering domains. Each scattering domain consists of several hundred dipoles. The dipoles are either uniformly arranged at a specific angle, which produces a specific angle-dependent polarization response, or randomly oriented to produce an unpolarized response. In order to read out the polarimetric information stored in the tags, the position and rotation of the radar barcodes needs to be determined. Our research reveals that using three reference elements and a novel decoding algorithm, a position- and rotation-tolerant readout is possible. To reduce distortions caused by the surface of the structure carrying the dipoles, different matching layer concepts were investigated. The novel chipless RFID tag concept is tested using a fully polarimetric W-band (75-110GHz) imaging radar. The implemented setup allows for a theoretical data capacity of 1.92bit/cm2 on a single layer PCB. In our measurements, we achieved a data capacity of 1.52bit/cm2. Utilizing the chosen tag size of 45mm×45mm resulted in a tag with a greater than 30 bit data capacity, which is an excellent value for chipless RFID.<br
Keywords: Chipless radio-frequency identification (RFID); image processing; millimeter wave; radar imaging; RFID

Chipless UWB TDR RFID Landmark-Based Positioning Using Polarimetric Filtering - Pöpperl, Maximilian; Dobrev, Yassen; Gottinger, Michael; Mandel, Christian; Jakoby, Rolf; Vossiek, Martin (International Conference on Microwaves for Intelligent Mobility, 2016)
lhft_intern.bib::Poepperl2016b

Circular Polarization Millimeter-Wave SAR Imaging using 3D-Printed Helix Antennas - Ullmann, Ingrid; Root, Konstantin; Lomakin, Konstantin; Gold, Gerald; Gottinger, Michael; Helmreich, Klaus; Vossiek, Martin (SPIE Security + Defense Forum, 2020)
We propose the use of 3D-printed helix antennas for millimeter-wave radar imaging. This concept is promising for a number of reasons: Additive manufacturing involving 3D-printing is a relatively cost efficient fabrication technique and offers increased geometrical freedom of design compared to conventional manufacturing processes. From an imaging point of view, using helix antennas is advantageous because of the circular polarization the antennas emit. That way, imaging thin dipole-like structures is possible regardless of their orientation. In contrast, imaging systems using linearly polarized antennas are unable to image dipoles orientated orthogonally to their polarization direction. Radar systems using circular polarization additionally enable polarimetric imaging and decomposition. In security screening this can achieve a higher classification accuracy in discriminating threat objects and reduce false alarms. Furthermore, the thin helix antennas (typical coil diameter: ca. 1.5 mm) can be mounted very closely to each other, which is interesting for array design. A security screening example was investigated for demonstration: A cardboard box with metallic and dielectric threat objects was screened at 70 GHz – 90 GHz by a quasi-monostatic synthetic aperture radar consisting of two 3D-printed helix antennas, one right-hand and one left-hand circularly polarized. As a reference, the same object was screened with split-block linearly polarized horn antennas. With the proposed setup, the resolution of the reconstruction images was comparable to that of the reference system. However, the circular polarization was able to depict thin structures in a better fashion than the linearly polarized reference system.

Classification of rheumatoid arthritis from hand motion capture data using machine learning - Fleischmann, Sophie; Holzwarth Correa, Vivien; Coppers, Birte; Sadeghi, Misha; Richer, Robert; Kleyer, Arnd; Simon, David; Bräunig, Johanna; Vossiek, Martin; Schönau, Verena; Schett, Georg; Koelewijn, Anne; et al. (13. Kongress der Deutschen Gesellschaft für Biomechanik (DGfB), 2024)
Intro Classifying movement restrictions in patients with rheumatoid arthritis (RA) is challenging. Machine learning (ML) can identify patterns in the data that cannot be captured with statistical tools. Aim To test the feasibility of classifying RA patients and controls from hand motion capture data using automatic feature extraction (AFE) and ML and to evaluate if a larger feature set improves the performance. Methods 24 RA patients (ACR/EULAR 2010 criteria) and 23 controls performed tipping and flexion of the hand [1], which was captured by an optoelectronic measurement system at 100 Hz with 29 reflective markers placed on the hand dorsum. We extracted the 3D trajectories, expressed relative to the central wrist marker and normalized to the hand length, of 24 markers on one hand (excluding thumb markers). After linearly interpolating missing values we filtered the data using a 4th-order Butterworth filter at a 6 Hz cut-off frequency and extracted a minimal and extensive feature set from the hand trajectories using the AFE package tsfresh [2]. We compared 4 classifiers in combination with scaling and dimensionality reduction (Fig 1). For every combination of algorithms, we trained a model using a stratified 10-fold nested cross-validation (CV). Hyperparameters were found from an inner five-fold CV on the respective train set using grid search. We report the accuracy of the best model averaged over the 10 folds. Results The best accuracy was 68.2% for flexion and 62.7% for tipping (Fig 2). Using the extensive instead of the minimal feature set led to no major change in accuracy. Summary The classification performance based on AFE was below the anticipated level of accuracy (>70%), likely due to the small dataset with limited data quality. We currently evaluate the approach on a more consistent, larger dataset and include expert features in addition to AFE. References [1] Phutane et al., Sensors, 21(4), 1208, 2021 [2] Christ et al., Neurocomputing, 307, 72-77, 20

Classification Strategies for Radar-Based Continuous Human Activity Recognition with Multiple Inputs and Multi-Label Output - Ullmann, Ingrid; Guendel, Ronny G.; Kruse, Nicolas Christian; Fioranelli, Francesco; Yarovoy, Alexander (IEEE Sensors Journal, 2024)
Fall detection systems can play an important role in assuring safe independent living for vulnerable people. These sensors not only have to detect falls, but also have to recognize uncritical, normal activities of daily living in order to differentiate them from falls. Radar sensors are very attractive for human activity recognition thanks to their contactless capabilities and lack of plain videos recorded. In this paper, a novel approach to recognize single activities in a continuous stream of radar data is proposed, whereby the stream is divided into windows of fixed length and then multi-label classification is used to recognize all activities taking place in these time segments. While the initial feasibility of this approach was presented in an earlier contribution presented at the 2023 IEEE SENSORS conference, in this extended work additional in-depth studies on critical parameters are performed. Specifically, multiple combinations of different radar data domains/representations (e.g., range-time maps, range-Doppler maps and spectrograms) and different radar nodes in a network of five cooperating sensors are considered as inputs to two considered multi-label classification networks. Additionally, a parametric study on the probability thresholds of the networks to assign labels to specific classes is also performed.
CRIS-Team Scopus Importer:2024-08-02
Keywords: Activities of daily living; deep learning; Doppler effect; Fall detection; Human activity recognition; human activity recognition; Legged locomotion; multi-label classification; radar; Radar; Sensors; Spectrogram

Clock Synchronization in Wireless Positioning and Sensor Networks - Kirsch, Fabian; Vossiek, Martin (IEEE Radio & Wireless Symposium, Workshop on Radar and positioning systems: innovative approaches and future trends, 2009)
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.clocks

Close range ISAR imaging with target velocity determination for security screening applications - Root, Konstantin; Ullmann, Ingrid; Gmehling, Stefan; Vossiek, Martin (Emerging Imaging and Sensing Technologies for Security and Defence VI SPIE Security + Defence, 2021)
State-of-the-art personnel screening systems reconstruct images by using multiple-input-multiple-output (MIMO) radars, which require a large number of transmit and receive channels along a two-dimensional array. We propose a novel concept for security screening which does not require the person to stand still and only employs a one- dimensional array: Our approach is built on the use of inverse synthetic aperture radar (ISAR) imaging based on a vertical line array. This means that the moving person inversely samples a synthetic aperture along the horizontal dimension. In order to reconstruct an image by the ISAR principle, the test subject's velocity relative to the radar aperture needs to be known. Therefore, we employ an additional radar module which measures the person's velocity, assuming that the person is moving parallel to the aperture plane. Experiments with a mannequin carrying threat objects were performed. The mannequin was moved on a traversing rail with 1 m/s and its velocity was estimated by a commercial radar module emitting a chirp sequence signal. The estimation was in very good accordance with the rail's real moving speed. With the determined target velocity an image was reconstructed along the horizontal direction by the ISAR principle. Along the vertical direction, the focusing was performed using a MIMO line array of 45 transmitter and 24 receiver channels with a total height of 60 cm. That way, and by employing broadband signals (70 GHz - 80 GHz), three-dimensional high-resolution images were obtainable. Promising results were obtained from the measurements and different threat objects were made visible.
Keywords: Radar; Velocity measurements; Image resolution; Synthetic aperture radar; Imaging arrays; Radar imaging; Scanners

CNN Based Road Course Estimation on Automotive Radar Data with Various Gridmaps - Prophet, Robert; Jin, Yi; Fuentes-Michel, Juan-Carlos; Deligiannis, Anastasios; Weber, Ingo; Vossiek, Martin (2020 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM), 2020)
Automotive radar is a promising technology with regard to path planning, since radar systems offer a comparatively long range and are robust against bad weather conditions. In this paper, we use Convolutional Neural Networks (CNN) to determine the current road course from radar point clouds. For this purpose, we first transform the radar point cloud into various gridmaps, which then serve as an input for the CNN. The quality of the road course estimation is evaluated using a test dataset. Exemplary test results showed an average deviation of less than 91 cm at a range of 100 m between the ground truth and the estimated road course. These excellent results prove that CNN processing of radar measurements is an attractive option for reliable and precise road course estimatio

CO and CO_2 Concentration Measurements inside of Sealed CO_2 Laser Tubes: An Application Example for a Fiber-Optic Diode Laser Gas Sensor - Engelbrecht, Rainer; Schulz, R.; Striegler, Arne (16th Int. Conference on Lasers and Electrooptics CLEO Europe, München 23.- 27. Juni, 2003)
In this paper, we demonstrate the use of fiber-optic tunable diode laser spectrometer within the thermal tuning range from 1581 nm to 1584 nm a CO/CO/sup 2/ absorption line pair with a frequency separation of 3.65 GHz between the line centers for the measurements of CO and CO/sub 2/ concentrations inside the sealed CO/sub 2/ laser tubes. © 2003 IEEE.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.coandc

Coherent Automotive Radar Networks: The Next Generation of Radar-Based Imaging and Mapping - Gottinger, Michael; Hoffmann, Marcel; Christmann, Mark; Schütz, Martin; Kirsch, Fabian; Gulden, Peter; Vossiek, Martin (IEEE Journal of Microwaves, 2021)
Imaging radar is a key perception technology for automotive and industrial applications. A lot of progress has been made with high channel count systems, deploying, for example, 12 transmit and 16 receive channels with cascaded monolithic microwave integrated circuit solutions. Nevertheless, fully automated driving requires even higher angular resolution for drive-under/drive-over decisions and exact predictions of object trajectories in dense urban driving scenarios. Both problems can be solved by increasing the antenna size and building larger radars. However, there is a physical limit to what can be placed on the front of a car, and manufacturing very large arrays is quite difficult. Thus, coherent automotive radar networks are a way to achieve high spatial resolution and obtain the complete velocity vector of an object from a single measurement. This solution is commercially attractive, as the sensor can remain relatively small, and complexity can be moved from the physical hardware to algorithms and processing. Two different test setups, each comprised of two multiple-input multiple-output radar units in the 76–77 GHz band, are presented in this article. To obtain azimuth and additional elevation information, the setups use a 1D and a 2D antenna array, respectively. Processing-based coherent evaluation is employed to create an additional radar image with doubled azimuth resolution and improved signal-to-noise ratio and to enable the estimation of vectorial target velocities. These benefits are presented and compared with optical reference images in traffic scenario

Coherent Full-Duplex Double-Sided Two-Way Ranging and Velocity Measurement Between Separate Incoherent Radio Units - Gottinger, Michael; Kirsch, Fabian; Gulden, Peter; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2019)
This paper presents a novel coherent full-duplex(FD) double-sided two-way ranging (CFDDS-TWR) techniquefor wireless locating and velocity measurement between separateradio units. The idea presented here is a quantum leap inwireless locating since it enables coherent ranging, continuousphase tracking, and velocity measurement between wirelessunits that operate incoherently with separate low-cost crystaloscillator clock sources. Frequency modulated continuous wavechirp sequences are exchanged in a FD manner between tworadio units. The signals transmitted from two radio units arereceived, respectively, by each of the two units and down-converted in a mixer with the receiver’s own transmit signalto generate a beat signal in each unit. The two beat signalsare then processed together, after one beat signal is transmittedto the partner unit. Phase coherent range and Doppler phasemeasurements can be conducted between incoherent radio units.The presented CFDDS-TWR technique also offers options forreducing noise-like distortions caused by mixing the productsof uncorrelated phase noise. We show both analytically andexperimentally that the described compensation method reducesthe noise level and enhances the dynamic range of the ranging sig-nals tremendously—as evidenced by an improvement of around24 dB in our results. These unique signal and synchronizationproperties show that the CFDDS-TWR method is a highlyaccurate measurement approach. Results acquired with a 24-GHztest system in a 7- to 17-m range demonstrate a standarddeviation in range and velocity of 0.25 mm and 0.05 mm/s,respectivel
Keywords: Wireless communication; Chirp; Clocks; Synchronization; Doppler radar; Distance measurement; Doppler radar; full-duplex (FD); phase measurement; phase noise (PN); radar; radio navigation; synchronization; transponders; wireless localization

Coherent multimode-fiber MIMO transmission with spatial constellation modulation - Bulow, H.; Al-Hashimi, H.; Schmauß, Bernhard (Optical Communication (ECOC), 2011 37th European Conference and Exhibition on, 2011)
lhft_intern.bib::Bulow2011a

Coherent Signal Processing for Loosely Coupled Bistatic Radar - Gottinger, Michael; Gulden, Peter; Vossiek, Martin (IEEE Transactions on Aerospace and Electronic Systems, 2021)
Sensitivity and performance of homodyne radar are notably improved if the phase noise terms of transmit and receive signals are correlated and cancelled out by the receiver. However, in a bistatic setup with separate oscillators, this correlation is inherently not given. To achieve a good carrier phase and phase noise coherency it is required to transmit a radio frequency (RF) reference e.g. by using high-quality RF cables, optical fibers or wireless point-to-point links. All these options are complex, costly and prone to distortions and signal delay variations. Sharing a clock signal is also barely helpful, since even small distortions of this reference are converted to notable uncorrelated phase noise in the radar signal synthesizers. In this paper, a novel full-duplex system concept and signal processing scheme is presented that solves the above-mentioned problems completely. This concept allows for coherent measurements within a bistatic radar setup, even if the two radar stations are only loosely coupled employing a simple clock-rate adjustment. By theory and experimental results with bistatic frequency modulated continuous wave (FMCW) radar it is shown that our concept allows for bistatic measurements with the same sensitivity and performance that is usually know from homodyne radar systems. To the authors' best knowledge, this is the first time that phase noise coherent measurements in a bistatic multiple-input multiple-output (MIMO) radar setup are shown. This concept paves the way for advanced netted radar setups e.g. in automotive radar and applications with large apertures or baselines or multi-perspective coherent tomographic measurement

Collaborative Research Centre 694 “Integration of electronic components into mobile systems”–Motivation and survey - Weckenmann, Albert; Schmidt, Lorenz-Peter; Bookjans, M. (Science Direct, Physics Procedia 5, 2010)
lhft_intern.bib::Schmidt2010

Combination of All-Optical 2R Signal Regeneration with Fiber-Based Retiming - Schmauß, Bernhard; Striegler, Arne (Photonics Technology Letters, IEEE, June, 2005)
We present all-optical signal regeneration using fiber-based retiming to overcome limitation by intrachannel cross-phase modulation-induced timing jitter in 2R regenerated transmission systems. As timing shifts of the optical pulses depend on the sign of the accumulated dispersion, timing jitter can be balanced out by a short piece of fiber with inverse sign of accumulated dispersion as the preceding transmission span. Timing jitter is cancelled out completely. Remaining amplitude jitter and ghost pulses are reduced by 2R-regeneration based on self-phase modulation. Limitation by amplitude jitter of the retiming stage and limitation by timing jitter of the 2R-regeneration cancel out each other. Numerical simulations show that maximum transmission distance is enhanced significantly. © 2005 IEEE.
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.combin
Keywords: All-optical; Regeneration; Retiming

Combined distributed Raman and Bragg fiber temperature sensing using incoherent optical frequency domain reflectometry - Köppel, Max; Werzinger, Stefan; Ringel, Thomas; Bechtold, Peter; Thiel, Torsten; Engelbrecht, Rainer; Bosselmann, Thomas; Schmauß, Bernhard (Journal of Sensors and Sensor Systems, 2018)

Combining radar and ultrasound imaging for surface echo compensation and augmented visibility of interior structures in NDT applications - Ullmann, Ingrid; Schür, Jan; Vossiek, Martin (13th European Conference on Non-Destructive Testing (ECNDT), 2023)
Millimeter-wave radar imaging is a promising technique in non-destructive testing. When a small material defect is located closely to the test object’s surface, the strong reflection caused by the air-material interface can overlap with the defect’s weak reflection and mask it. If the image resolution is not sufficient, the defect cannot be resolved and will not be recognizable in the reconstruction image. To solve this problem, surface echo compensation techniques have been invented. However, these techniques are usually restricted to planar surfaces, which for most applications is not the case. This article presents a technique for surface echo compensation of arbitrarily shaped objects. We propose to combine radar and air-coupled ultrasound. Since air-coupled ultrasound is not able to penetrate solids, an air-coupled ultrasound imaging system is only able to detect the surface of a solid object. The idea of our proposed concept is to employ the ultrasound signal to compensate for the surface echo in the radar signal. The proposed method is based on the idea of using signals of equal wavelengths for both wave types and an amplitude calibration. Then, the resulting signals for radar and ultrasound are formally equal, which makes it possible to directly combine them numerically. That way, a modified radar image can be obtained which only contains the reflections from the inside and highlights interior defect

Combining Run-Length Encoding Preprocessing With Lempel-Ziv-Markov Algorithm to Enhance Compression for Automotive Radar Data - Rückert, Rainer; Herglotz, Christian; Sura, Oliver; Ninov, Youliy; Kaup, André; Vossiek, Martin (2025 16th German Microwave Conference (GeMiC), 2025)

Comb-Locked Terahertz Spectroscopy of Critically Coupled Ultrahigh-Q Whispering-Gallery Mode Resonators - Mueller, Sebastian; Puppe, Thomas; Mayzlin, Yuriy; Wilk, Rafal; Schmauß, Bernhard; Vogt, Dominik Walter (2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, 2023)
We present a novel frequency domain spectrometer, which is based on two external cavity diode lasers (ECDL) locked to a fibre-based erbium frequency comb, the repetition rate frep of which is in turn referenced to a radio frequency (RF-) oscillator. By using an external endless frequency-shifter [1], one of the lasers is detuned by frequencies up to 10 THz, limited only by the spectral width of the comb. Within the locking bandwidth, the stability and phase noise of the RF reference is transferred to the difference frequency between both ECDLs [2].
CRIS-Team Scopus Importer:2023-12-01

Commercial applications of mm-waves (invited paper) - Schmidt, Lorenz-Peter (ESA Workshop on Millimeter Wave Technology and Applications, 1995)
lhft_intern.bib::Schmidt33

Compact 150 GHz and 300 GHz Dual-Band On-Chip Antenna for Future Communication and Sensing Applications - Pfahler, Tim; Schür, Jan; Vossiek, Martin (2024 IEEE Wireless and Microwave Technology Conference (WAMICON), 2024)
This paper presents the design and measurement of an on-chip dual-band patch antenna which enables simultaneous radiation in the 110–170 GHz and 220–325 GHz frequency band. In addition to frequency diversity, the feed ports are polarization decoupled, thus minimizing crosstalk. Parasitic mode suppression as part of a patch cavity analysis was used to achieve the functionality of the antenna. The measured −10 dB matching bandwidth is 6.5 GHz in the lower and 15.6 GHz in the upper frequency band, respectively. In particular, the simulated peak antenna gain of 3 dBi at 295 GHz can compensate for the higher path losses at sub-THz frequencies. The unique feature of the proposed antenna, compared to other dual-band antennas, is the ability of λ 0 /2 spacing for phase array applications in both frequency bands due to the geometrical compactness of the antenna.<br
Keywords: Antenna measurements; Wireless communication; Phased arrays; Wireless sensor networks; Patch antennas; Dual band; Microwave antenna arrays; Antennas; array; dual-band; dual-polarization; millimeter wave integrated circuits; on-chip; terahertz

Compact and Broadband 300 GHz Three-Element on-chip Patch Antenna - Pfahler, Tim; Vossiek, Martin; Schür, Jan (IEEE Radio and Wireless Symposium, RWS, 2023)
This paper presents a 300 GHz three-element on-chip patch antenna with lateral coupled parasitic patch elements. The achieved matching bandwidth is 26 GHz. The key advantage of the proposed design is the resulting broadband characteristic with simultaneous lateral geometric compactness of the antenna to fit into an array with λ0/2-spacing at the target frequency. Due to this lateral compactness and the resulting greater gap between adjacent array elements the mutual coupling can be minimized. A realized gain larger than 0 dBi is achieved over a bandwidth of 21 GHz with a simulated peak antenna gain of 1.7 dBi at 295 GHz. Moreover, the beam pattern is frequency independent without a pattern-tilt/distortion over the considered frequency bandwidth which makes the antenna particularly appropriate for beam steering on MIMO antenna-array applications in broadband Sub-THz communication and high-resolution radar sensing.
Created from Fastlane, Scopus look-up
Keywords: antennas; array; millimeter wave integrated circuits; MIMO; on-chip; terahertz

Compact and Stable 2.5 THz Local Oscillator Laser System for Long Period Operation - Hocke, Ralf; Engelbrecht, Rainer; Maier, M.; Raum, Michael (3rd International Workshop on Terahertz Electronics, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.compac

Compact and Stable 2.5 THz-LO-Laser System for long Period Operation - Hocke, R; Engelbrecht, Rainer; Maier, M; Raum, M (1995)
lhft_intern.bib::thirty_years_LHFT_361

Compact Low-Loss 2.4GHz ISM-Band SAW Bandpass Filter on the LTCC Substrate - Novgorodov, V.; Freisleben, S.; Hornsteiner, J.; Schmachtl, M.; Vorotnikov, Borys; Heide, Patric; Vossiek, Martin (Asia Pacific Microwave Conference 2009, 2009)
This paper describes a design of a surface acoustic wave (SAW) ladder-type bandpass filter (BPF) for 2.4-2.5GHz ISM-band, based on the low temperature co-fired ceramic (LTCC) substrate, which can be used in 802.11b/g wireless LAN and Bluetooth applications. It obtains an excellent state-of-the-art performance in the ultra small package. The proposed architecture is based on a combination of SAW and low temperature co-fired ceramic (LTCC) technologies, where the multilayer LTCC substrate is used for integration of matching and passband-driving elements and for obtaining additional transmission zeros. It is comprised of three series and two parallel SAW resonators, realized on the LiTaO3 piezoelectric substrate and connected accordingly to a ladder-type T-topology circuit design, and an additional resonator to obtain an attenuation at 2.57-2.62 GHz IMT-E (TDD) band. Two input/output matching inductors and three additional inductors, permitting to obtain a sufficient suppression level at 2.11-2.17 GHz UMTS (DL) band and harmonics, are completely integrated within ceramic. The described bandpass filter has ultra small dimensions of 1.1 x 1.4 x 0.9 mm, very low insertion losses of -1.5 dB max in the passband. This fully matched SAW bandpass filter has achieved excellent selectivity performance with the up-to-date smallest package size. ©2009 IEEE.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.compac
Keywords: Bandpass filter (BPF); Coexistence; Ladder-type; Low temperature co-fired ceramic (LTCC); Surface acoustic wave (SAW); System-in-package (SIP); Wireless local area network (WLAN)

Compact Submillimeter Wave Ring Laser System for Field Experiments - Janker, R; März, M; Voigt, C; Brand, Hans (1989)
lhft_intern.bib::thirty_years_LHFT_262

Compact Substrate Integrated Wireless Cure Monitoring Sensor for Epoxy Resin - Groh, Jannis; Lee, William; Schür, Jan; Distler, Felix; Vossiek, Martin (48th European Microwave Conference (EuMW 2018), 2018)

Comparative Noise Characterization and Conversion Loss Measurements of Schottky Diode Mixers at 600 GHz - Schür, Jan; Biber, Stephan; Cojocari, O.; Schmidt, Lorenz-Peter; Hartnagel, H. (30th Workshop on Compound Semiconductor Devices and Integrated Circuits, 2006)
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.compar

Comparison of Different Approaches for Identification of Radar Ghost Detections in Automotive Scenarios - Jin, Yi; Prophet, Robert; Deligiannis, Anastasios; Weber, Ingo; Fuentes-Michel, Juan-Carlos; Vossiek, Martin (IEEE National Radar Conference - Proceedings, 2021)
This paper focuses on the frequently occurring issue of automotive radar sensors: ghost detection. Three data-based approaches, namely random forest, convolutional neural network (CNN), and PointNet++, are adopted to identify ghost detection. Evaluated with the same dataset, random forest and PointNet++, with more than 95% accuracy, are evidently better than CNN in not only city but also motorway scenarios. Furthermore, the influence of various features for each classifier is also analyze

Comparison of different control loop concepts for direct distance measurement using photonic mixing devices (PMD) - Becker, Dirk; Gulden, Peter; Vossiek, Martin (IEEE Sensors 2002. First IEEE International Conference on Sensors, 2002)
This paper presents two different control loop approaches for distance measurement with photonic mixing devices (PMD). Possible all-analog implementations are pointed out, and measurements with two different loop types using our laboratory PMD system are provided. It is shown that the PI control loop implementation reaches distance accuracy comparable to previous modulation methods, but on the other hand suffers from present offsets of the PMD. For the second method, the steepest descent algorithm, contrary results are obtained. This method is not susceptible to offset variations, but requires a fairly high SNR to converge. Finally the requirements for all-analog closed loop implementation imposed on the next generation of PMD elements are pointed out.
UnivIS-Import:2015-04-16:Pub.2002.tech.IE.LEH.compar
Keywords: Electro-optical control loop; PI-controller; PMD distance measurement; Steepest descent

Comparison of DPSK and OOK Modulation Format in 160 Gbit/s Transmission Systems - Ferber, S.; Ludwig, E.; Börner, B.; Wietfeld, André; Schmauß, Bernhard; Berger, J.; Schubert, C.; Unterbörsch, G.; Weber, H. G. (Electronics Letters, 2003)
Single-polarisation 160 Gbit/s OTDM transmission over 3 × 80 km dispersion-managed SLA fibre using DPSK and OOK modulation is reported. The influence of the fibre input power is experimentally and theoretically investigated. A significant advantage for DPSK is revealed.
UnivIS-Import:2015-03-09:Pub.2003.tech.IE.LEH.compar

Comparison of local transmit antennas for extremity imaging in MRI - Schöpfer, Johanna; Biber, Stephan; Vossiek, Martin (2015)