Novel UHF-RFID Listener Hardware Architecture and System Concept for a Mobile Robot Based MIMO SAR RFID Localization - Gareis, Matthias; Hehn, Markus; Stief, Patrick; Körner, Georg; Birkenhauer, Christoph; Trabert, Johannes; Mehner, Tom; Vossiek, Martin; Carlowitz, Christian (IEEE Access, 2020)
In this paper, we introduce an ultra-high frequency radio frequency identification (UHF-RFID) mobile robot platform that is capable of performing fully autonomous inventory taking and stocktaking by providing three-dimensional (3D) product maps and thus making possible the concept of a smart warehouse. The proposed novel hardware architecture consists of an eight-channel UHF-RFID-listener for parallel signal phase recovery, including two different carrier leakage suppression circuits and a correlation decoder for each channel for the tag signal, which can handle a backscatter link frequency (BLF) deviation of up to 22 % to decode the tag data. The system also uses eight parallel channels for multiple-input multiple-output (MIMO) localization. For the system evaluation we labeled clothes stored in a warehouse with tags and generated their product map. The proposed localization algorithm is based on a synthetic aperture radar (SAR) MIMO approach that needs exact knowledge of the antenna positions and, therefore, of the driven trajectory. This position is provided by the robot, which takes advantage of a simultaneous localization and mapping (SLAM) algorithm, determining the position with 1 cm accuracy while generating two-dimensional (2D) maps of the surroundings. We placed ten tags at known positions to assess the system’s performance and were able to locate these tags within a root mean square error (RMSE) of 1.45 cm in 3

Novel ultra-compact quad-band System-in-Package (SiP) module with IC embedded in substrate based on SESUB technology - Sieroshtan, V.; Sevskiy, Georgiy; Komakha, P.; Aleksieiev, O.; Burygin, A.; Chayka, O.; Ruban, O.; Shevelov, M; Kato, K.; Horibe, A.; Fujioka, H.; Ruffing, K.; et al. (45th Annual International Symposium on Microelectronics, IMAPS 2012, 2012)
This paper presents a novel ultra-compact System-in-Package (SiP) module with highly integrated wireless connectivity devices combining a set of 4 standards: WLAN, Bluetooth, FM and GPS. Besides an IC, the SiP module consists of RF filters, SMD components and a Single-Chip RF Front-end. The main IC is embedded inside the substrate and basics of SESUB technology are described. For electromagnetic compatibility and physical protection a metal EMI shield has been used. The total size of solution presented is 8.0×7.5×1. 3mm demonstrating significant miniaturization over current module technology. The embedding process and SiP module routing has shown benefits in electrical and mechanical performance.
Keywords: Integrated circuits; Module; SESUB; Substrate; System-in-package (SiP)

Numerical and Experimental Investigation of a Fiber-Optic Sensor Consisting of a Fiber Bragg Grating in a Two-Mode Fiber for Simultaneous Sensing of Temperature and Strain - Siekiera, Alexander; Engelbrecht, Rainer; Schmauß, Bernhard; Buethe, Lars (AMA Conferences 2013, OPTO, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.numeri

Numerical Calculation of Stimulated Brillouin Scattering and its Suppression in Raman Fiber Amplifiers - Engelbrecht, Rainer; Bayer, M.; Schmidt, Lorenz-Peter (16th Int. Conference on Lasers and Electrooptics, CLEO Europe, München, 23.- 27.Juni, 2003)
In this paper, simulated Brillouin scattering in Raman fiber amplifier was numerically calculated. The theoretical results show that much more power could be transferred from the pump to the signal in Raman fiber amplifier with no SBS and Brillouin frequency shift in a given fiber depends on temperature and on mechanical strain. And spatially variable longitudinal strain distribution in standard fibers for SBS suppression in active devices was proposed. © 2003 IEEE.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.numeri

Numerical Evaluation of the Functional Boundaries of Digital Backward Propagation Algorithm for Mitigating Non-linear Impairments in Phase Encoded Transmission - Asif, Rameez; Lin, C.; Holtmannspötter, Michael; Schmauß, Bernhard (Journal of Physics Procedia, Special Issue LANE Conference, 2010)
lhft_intern.bib::Asif10

Numerical Link Design Optimization of Single Channel 160 Gbit/s Transmission based on ODTM Technology - Wietfeld, André; Striegler, Arne; Schmauß, Bernhard (Workshop der ITG Fachgruppe 5.3.1., 2002)
UnivIS-Import:2015-04-16:Pub.2002.tech.IE.LEH.numeri_1

Numerical Modeling of Intracavity Spectral Broadening of Raman Fiber Lasers - Hagen, Johannes; Engelbrecht, Rainer; Welzel, Oliver; Siekiera, Alexander; Schmauß, Bernhard (IEEE Photonics Technology Letters, 2007)
Raman fiber lasers (RFLs) are efficient light sources at frequencies where no other comparable all-solid-state sources are available. Especially if fiber Bragg gratings (FBGs) withnarrow bandwidths are used, the bandwidth of the Stokes light is strongly broadened by Kerr nonlinearities like four-wave mixing (FWM), and self- and cross-phase modulation (SPM, XPM). In this letter, we discuss an exact numerical model to calculate the spectral behaviour of RFLs and show its application to determine the effective reflectivity of the FBGs. The model is based on a combination of the nonlinear Schroedinger equation including dispersion, FWM, SPM, and XPM with a shooting method to solve the power steady-state equations for RFLs. Numerical results are in good agreement with measurements. © 2007 IEEE.
UnivIS-Import:2015-03-09:Pub.2007.tech.IE.LEH.numeri
Keywords: Four-wave mixing (FWM); Raman fiber laser (RFL); Spectral broadening

Numerical Optimisation of a 160 Gbit/s Receiver based on an optical Time Domain Demultiplexer - Wietfeld, André; Schmauß, Bernhard (Conf. Proceedings NOC, 2002)
UnivIS-Import:2015-04-16:Pub.2002.tech.IE.LEH.numeri

On the Advantages of Coherent Automotive Radar Networks for Occupancy Gridmapping - Sura, Oliver; Euler, Mario; Heidbrink, Max; Hoffmann, Marcel; Gulden, Peter; Vossiek, Martin (2024 21st European Radar Conference (EuRAD), 2024)
Autonomous driving requires a robust and detailed perception of the environment even under harsh environmental conditions. Radar sensors can play an integral part in reaching this goal. However, compared to lidar, radar data suffer from lower angular resolution and sparser and noisier point clouds. While occupancy gridmapping has proven to be a valuable mapping tool for clutter-prone point clouds, coherent radar networks provide a promising solution for high-resolution radar imaging. Consequently, this paper evaluates the use of a coherent radar network in combination with occupancy gridmapping to demonstrate the benefit of a coherent bistatic radar network consisting of two stations compared to incoherently operating radar systems. It is demonstrated that the occupancy gridmaps obtained with the coherent network are superior to the standard incoherent system in terms of resolution, number of detected targets, and vectorial velocity estimatio

On the Kelvin Transformation in Finite Difference Implementations - Gold, Gerald (Electronics, 2020)
Finite difference operators were applied on a Delaunay mesh. This way it is possible to discretize a radial boundary that is used to perform a Kelvin mapping of an additional outer domain to virtually extend the computation domain to infinity. With an example two-wire problem, the performance of this approach is shown in comparison with a conventional calculation domain and with the analytical solution, respectively. The presented implementation delivers a more precise approximation to the real values and at the same time requires a smaller system of equations—i.e., allows for faster computation
Keywords: Delaunay mesh; FEM mesh; finite differences; infinite differences; Kelvin mapping; Kelvin transformation; open boundary; unbounded grid

On the Needlessness of Signal Bandwidth for Precise Holographic Wireless Localization - Lipka, Melanie; Brückner, Stefan; Sippel, Erik; Vossiek, Martin (EuRAD 2020 - 2020 17th European Radar Conference, 2021)
Microwave localization systems offer manifold advantages for applications in indoor environments where high freedom of movement hand-in-hand with robust tracking is mandatory. However, reliable live-tracking demands for high update rates and accurate positioning. But due to legal requirements the bandwidth is restricted and therefore the achievable range and multipath resolution is limited. In this paper, the performance of a holographic, Kalman filter based localization approach in microwave localization systems with reduced bandwidth is investigated. The accuracy is verified in an industrial scenario, holding severe multipath using a 24 GHz frequency-modulated-continuous-wave system. Based on experimental results it is shown that the holographic wireless localization technique enables 3D em-precision localization largely unaffected by the chosen signal bandwidth. This unique property is a great advantage compared to classic wireless locating approaches based on multilateration.
CRIS-Team Scopus Importer:2021-05-14
Keywords: Kalman Filtering; position measurement; radar signal processing

On the Performance of Holographic Extended Kalman Filters for Localization in Industrial Automation - Lipka, Melanie; Sippel, Erik; Brückner, Stefan; Vossiek, Martin ("Proceedings of the 2020 German Microwave Conference (GeMiC)", 2020)
Microwave localization systems are increasingly popular for the proceeding automation of logistics and modern factories, allowing for robust tracking of freely moving objects and workers. To enable reliable live-tracking, accurate positioning algorithms with high update rates are desirable. For this purpose, the holographic extended Kalman filter (HEKF) was presented in [1], combining low computational effort and an outstanding localization accuracy in the centimeter range. In this paper, the performance of the HEKF in a 24-GHz frequency modulated continuous wave system is evaluated. The impact on the accuracy of the evaluation frequency of the phase, reduced oversampling, and non-uniform movements are also investigate

On the performance of pulsed frequency modulated UWB local positioning systems - Ebelt, Randolf; Waldmann, Benjamin; Bauer, Georg; Aleksieieva, Anna; Eßwein, Alexander; Weigel, Robert; Vossiek, Martin (2011 IEEE MTT-S International Microwave Symposium, IMS 2011, 2011)
Recently, a novel ultra-wideband (UWB) local positioning concept based on pulsed frequency modulated (PFM) signals was introduced by the research groups of the authors of this paper. The current paper presents a detailed analysis of the performance - i.e. range and accuracy - of the proposed PFM-UWB approach. It is shown that with PFM-UWB an excellent coverage/range can be achieved. It is also shown that for high precision ranging a VCO with good phase-noise performance is needed. Based on simulations and measurement results the theoretical findings are verified. The results confirm that PFM-UWB allows for accuracy in the mm-range and a maximum range of more than 100 m with a measuring time of only 1 ms. © 2011 IEE
Keywords: radar; radio navigation; radio position measurement; transponders; Ultra-wideband (UWB)

Open Semiconductor Waveguide for Millimeter Wave Application - Karg, R; Ermert, H; Brand, Hans; Appelhans, G (IEEE, 1976)
A rectangular dielectric semiconductor waveguide is theoretically investigated by transverse mode matching methods. In an experiment the resistivity of the semiconductor material is changed by illuminating with a GaAs laser beam. Depending on the configuration and intensity of the light spot the waveguide behaves like a termination or a short. This effect is controllable in position and time. In a further step the radiation from a local inhomogeneity in an open structure is intentionally used for generating a light-controlled radiating elemen
lhft_intern.bib::thirty_years_LHFT_36

Optical Networks - Bandwidth without Limits? - Schmauß, Bernhard (Tutorial on DWDM Transmission at Networks, Munich, 2002)
UnivIS-Import:2015-04-16:Pub.2002.tech.IE.LEH.optica

Optical Power Transient Suppression by a Dynamic Broadband Attenuator Based on the Raman Effect - Holtmannspötter, Michael; Schmauß, Bernhard (Optical Fiber Communication 2008, 2008)
An optical attenuator based on the Raman Effect is presented which is shown to provide dynamic and broadband suppression of channel power transients in WDM transmission systems, without affecting the normal operation mode. ©2007 Optical Society of America.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.optica

Optical signal Regeneration at Different Modulation Formats - Schmauß, Bernhard; Striegler, Arne; Meißner, Markus (Proceedings of SPIE, 2004)
Optical transmission systems made impressive progress in the field of system capacity, reach and flexibility. Beside all improvements achieved so far, signal distortion on the one hand side and noise accumulation on the other hand side are the limitations of optical transmission systems. In terms of signal distortion besides advanced link design strategies optical regenerators are of high interest for signal conditioning along a fiber link. Furthermore the upcoming techniques of advanced modulation formats build a basis for further improvement of transmission quality that ends up with even higher reach, higher robustness against transmission impairments, lower signal to noise requirements etc. In this talk the current status of research in the field of optical signal regenerators suitable for signal regeneration for different modulation formats will be reviewed and presented, where we restrict our analysis to 2R regenerators. The focus will be put on regenerators taking advantage of non linear optical effects in order to improve signal quality. The main challenge is the treatment of phase modulated signals within regenerators. Especially the differential phase shift keying (DPSK) modulation format or the duobinary modulation format are attractive candidates for such kind of regenerators for further improvement of DPSK based transmission systems. The paper will go through several regenerative concepts like non linear optical loop mirror (NOLM) based and cross phase modulation based regenerators in order to figure out their potential for advanced modulation format based systems.
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.optica
Keywords: Modulation Format; Optical Transmission; Regeneration

Optical Transient Suppression using Stimulated Raman Attenuation - Holtmannspötter, Michael; Stephan, C.; Onishchukov, Georgy; Leuchs, Gerd; Schmauß, Bernhard (ECOC, September, 2008)
Dynamic optical attenuation based on the Raman Effect is investigated experimentally. The suppression of optical power transients as they arise from dynamic processes of EDFAs is shown. © 2008 IEEE.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.optica_3

Optimales, skalierbares Ressourcenmanagement für modulare, gemischt analog-digitale Testsysteme - Uygur, Gürkan; Lu, Ping; Glaser, Daniel; Weichselgartner, Susanne; Helmreich, Klaus; Sattler, Sebastian; Lechner, Armin; Brenneke, Andreas (Tagungsband, 2009)
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.c3scha.optima

Optimally shaped reflectors for Gaussian beam transformation - Schildbach, Christian; Schmidt, Lorenz-Peter (IEEE Conference on Antenna Measurements & Applications (CAMA), 2014)
For focusing reflectors usually paraboloidal and ellipsoidal shapes are used, which are a first degree approximation to an optimal beam transformer. In this paper, the design of such an optimally shaped reflector is described, using basic numerical procedures and common CAD software. The complexity of the described procedure is not much higher than the design of paraboloidal or ellipsoidal reflectors. Measurement data is presented to confirm the functionality of the designed reflector at frequencies beyoned 200 GHz.
lhft_intern.bib::Schildbach2014

Optimal storage-aided wind generation integration considering ramping requirements - Xiang, Lin; Ng, Derrick Wing Kwan; Lee, William; Schober, Robert (2013 IEEE International Conference on Smart Grid Communications, SmartGridComm 2013, 2013)
Large-scale integration of intermittent wind energy can put a large burden on the utility company in balancing system demand and supply. As more and more dispersed wind energy suppliers connect to the system for electricity supply, the power system suffers from increased operation cost and risk caused by the discrepant interests of energy suppliers and the utility company. Energy suppliers may only concern about maximizing their own profits by pushing as much energy into the grid as possible, while neglecting the risk of steep ramps in wind generation. In this paper, exploiting the two-way communication capability in smart grid, we propose interactive ramp control of wind energy integration by aligning the individual pursuits of the energy suppliers and the utility company for social welfare maximization. The optimal wind energy integration and generator ramp control are investigated in an offline social welfare optimization problem assuming full knowledge of future wind energy and load demand. Moreover, the benefits of storage are exploited in our proposed storage-aided generation range adaption scheme to reduce the potential risk caused by inaccurate wind energy forecasts and the ramping latency of slow generators. Furthermore, a suboptimal storage-aided generation range adaption scheme with low computational complexity is presented for online control of wind integration when wind energy forecasts are unavailable. Our simulation results show that interactive ramp control is necessary to achieve efficient and secure wind energy integration and with the aid of storage, the power system's ramping capability can be improved at lower operation cost. © 2013 IEEE.
CRIS-Team Scopus Importer:2020-02-03
Keywords: Large-scale integration; Ramp control; Smart grid

Optimal Transmit Signal and Beamforming Design for Integrated Sensing and Power Transfer Systems - Mayer, Kenneth; Lotter, Sebastian; Shanin, Nikita; Brückner, Stefan; Vossiek, Martin; Cottatellucci, Laura; Schober, Robert (IEEE Open Journal of the Communications Society, 2025)
Integrating different functionalities, conventionally implemented as dedicated systems, into a single platform allows utilising the available resources more efficiently. We consider a frame-based integrated sensing and power transfer (ISAPT) system and propose the joint optimisation of the transmit beamforming vectors, the pulse duration, and the subframe durations to combine sensing and wireless power transfer (WPT) functionalities efficiently. In contrast to prior works, we adopt an accurate nonlinear circuit-based energy harvesting (EH) model. We formulate and solve a non-convex optimisation problem for an arbitrary number of EH receivers and sensing targets (STs). The objective is to maximise the weighted sum of the average harvested powers at the EH receivers while ensuring the echo signals reflected by the ST targeted in the corresponding subframe are received with sufficient power for estimating the range to the ST with a prescribed accuracy within the considered coverage region. A method to determine the optimal solution to the problem is derived and two efficient suboptimal schemes are proposed. The performance gap between the upper-bound and the suboptimal schemes is shown to be small. The codesign of the sensing and WPT functionalities and the resulting optimised beampatterns are studied in detail. For high sensing accuracy requirements, the joint transmit signal and beamforming design is found to differ significantly from the optimal transmit signals dedicated to either sensing or WPT. A dedicated transmit signal for WPT is shown to enhance ISAPT system performance when the sensing requirements are less stringen
Keywords: Wireless power transfer; Sensing; Integrated Sensing and Power Transfer; Optimisation

Optimization of a fast scanning millimetre-wave short range SAR imaging system - Gumbmann, F; Tran, H; Weinzierl, Jochen; Schmidt, Lorenz-Peter (European Microwave Conference October, 2007)
This paper presents the development of a W-band short range imaging system for security and non-destructive testing applications, which uses an unfocused measurement setup employing SAR algorithms in order to focus the image numerically. The active imaging system offers the possibility to get a broadband frequency response from each pixel in the measurement plane. For real-time applications a fast scanning, monostatic virtual antenna concept has been developed and optimized. The monostatic setup is demonstrated in two different configurations, on the one hand using a quasioptical, broadband diplexer with high decoupling between transmitter and receiver channel and on the other hand a very compact setup using a commercially available high directivity waveguide coupler. The measurement setups are compared with special respect to their RF-performance. Experimental results on specific test objects are presented to prove the performance of the fast short range SAR imaging syste
lhft_intern.bib::Gumbmann07a

Optimization of a nonlinear amplifying loop mirror for amplitude regeneration in phase-shift-keyed transmission - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE Photonics Technology Letters, 2007)
We present the numerical optimization of the transmission characteristics of a nonlinear amplifying loop mirror for amplitude regeneration of phase-encoded optical transmission formats. Adjusting the splitting factor, the amplifier gain and the phase bias, minimal phase distortions can be achieved while strong amplitude fluctuations are regenerated. The limiting effects of noise from the built-in amplifier and of amplified Rayleigh backscattering are also discussed. © 2007 IEEE.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.optimi
Keywords: 2R-regeneration; All-optical regeneration; Differential phase-shift keying; Nonlinear amplifying loop mirror

Optimization of Dispersion-Imbalanced Loop Mirror for Phase-Preserving Amplitude Regeneration - Röthlingshöfer, Tobias; Sponsel, Klaus; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE/LEOS Winter Topicals Meeting Series, 2009)
The adaptation and optimization of a dispersionimbalance loop mirror for phase-preserving amplitude 2R regeneration is shown by numerical simulations. Its performance has been evaluated for DPSK transmission. A 4.8dB Q-factor improvement has been demonstrated.
UnivIS-Import:2017-12-18:Pub.2009.tech.IE.LEH.optimi

Optimization of Fusion Algorithm for Hybrid Pedestrian Localization and Navigation - Wang, Haowei; Bauer, Georg; Kirsch, Fabian; Vossiek, Martin (9th Workshop on Positioning, Navigation and Communication 2012 (WPNC 2012), 2012)
Hybrid pedestrian localization based on multiple data sources is becoming more and more popular. Nevertheless, accurate and reliable pedestrian localization is still a challenge due mainly to their unpredictable movement. For some applications such as interactive museum guidance unpredictable pedestrian movement is a major obstacle to accurate localization. In this paper we introduce a novel fusion algorithm using best-neighbor rating. The algorithm reduces the accumulated error originating from unreliable sensor measurements and increases the efficiency by only evaluating the nearby cells of the last estimated position. Experimental results show that a mean error of less than 1.5 M is achievable in real-world scenarios. © 2012 IEE
UnivIS-Import:2015-04-16:Pub.2012.tech.IE.LEH.optimi
Keywords: Dead Reckoning; Inertial Sensor; Localization; Navigation; Sensor Fusion; ZigBee

Optimization of the Chromatic Dispersion Equalizer of a 43Gb/s Realtime Coherent Receiver - Geyer, J. C.; Bisplinghoff, A.; Duthel, T.; Fludger, C. R. S.; Schulien, C.; Schmauß, Bernhard (OSA Optics and Photonics Congress, Advanced Photonics, BGPP Topical Meeting, Karlsruhe, 21.-24. Juni, 2010)
lhft_intern.bib::Geyer10

Optimization of the Power Spectral Density of Raman-MOPAs using Fiber Bragg Gratings with Tunable Chirp - Hagen, Johannes; Engelbrecht, Rainer; Lins, Bastian; Schmauß, Bernhard; Grüner-Nielsen, Lars (OFC San Diego, 2008)
Fiber Bragg Gratings with a temperature induced chirp are used to control and optimize the power spectral density of a Raman-MOPA by influencing the FWM-based power dependent spectral broadening. © 2007 Optical Society of America.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.optimi

Optimized Brillouin Frequency Distributions for SBS Suppression in Active Fibers - Engelbrecht, Rainer; Schmauß, Bernhard (Optical Fiber Communication Conference, 2016)
Optimized distributions of the local Brillouin frequency to increase the SBS threshold in active fibers are derived analytically. Theoretical results on SBS suppression in fiber amplifiers for arbitrary gain distributions are show
lhft_intern.bib::engelbrecht2016optimized

Optimized coil design for magnetic local positioning systems - Hehn, Markus; Vossiek, Martin; Dollinger, Felix; Leo, Karl; Kheradmand-Boroujeni, Bahman; Ellinger, Frank (GeMiC 2018 - The 11th German Microwave Conference (GeMiC 2018), 2018)

Optimized digital backward propagation for phase modulated signals in mixed-optical fiber transmission link - Asif, M. R.; Lin, C.; Holtmannspoetter, M.; Schmauß, Bernhard (Optics Express, 2010)
lhft_intern.bib::Asif10a

Optimized method for achieving accurate signals for “True-Mode” S-parameter measurements - Schramm, Marcus; Hrobak, Michael; Schür, Jan; Schmidt, Lorenz-Peter; Konrad, Michael (45^th European Microwave Conference, 2015)
Due to the capabilities of modern vector network analyzers (VNAs), the usage of “True-Mode”-signals for characterizing and testing active differential devices is quite convenient. Nevertheless in cases, in which the device under test (DUT) and/or the measurement setup introduces a coupling between the required stimulus signals, current methods require some iteration time to achieve the desired phase and amplitude settings. In this paper a new approach will be introduced, which leads to an optimized testing time which can be crucial especially in industrial production tes
lhft_intern.bib::Schramm2015

Optimum splitting ratio for amplifier noise reduction by an asymmetric nonlinear optical loop mirror - Meißner, Markus; Rösch, Matthias; Korolkova, Natalia; Sizmann, Andreas; Schmauß, Bernhard; Leuchs, Gerd (Optical Communication, 2002)
UnivIS-Import:2015-04-16:Pub.2002.nat.dphy.optik.1optik.optimu

Optimum splitting ratio for amplifier noise reduction by an asymmetric nonlinear optical loop mirror - Meißner, Markus; Rösch, Matthias; Schmauß, Bernhard; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2005)
We theoretically and experimentally analyze the influence of the splitting ratio and the input power on the noise reduction capability of an asymmetric nonlinear optical loop mirror (NOLM) for different input noise levels. An easy method to calculate the optimum parameters for noise reduction is also presented. The best noise reduction is found at NOLM input powers at which the nonlinear transfer function has a slope close to zero. Additionally, the splitting ratio of the NOLM has to be adapted to its input noise level to suppress amplitude fluctuations effectively. Since the noise reduction by the NOLM is due to the Kerr nonlinearity, which has a timescale below a few femtoseconds, the noise reduction is applicable to short pulses in the picosecond and femtosecond range. This makes the NOLM applicable as an optical regenerator in an optical data transmission system at high bit rates, such as 160 GBit/s. © Springer-Verlag 2005.
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.optimu

Optimum splitting ratio for amplifier noise reduction vy an asymmetric nonlinear optical loop mirror - Schmauß, Bernhard; Meißner, Markus; Rösch, Matthias; Leuchs, Gerd (Applied Physics B, Febr., 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.optimu

Optimum Wavelength for Maximum Range of an OTDR for Strain Measurement with POF - Dengler, Simon Andreas; Engelbrecht, Rainer; Schmauß, Bernhard (Optical Sensors: Proceedings Optica Sensing Congress 2023, AIS, FTS, HISE, Sensors, ES 2023, 2023)
With polymer optical fibers (POF), optical time domain reflectometry (OTDR) can be used to measure strain in soil spatially resolved. We discuss the signal to noise ratio (SNR), find the optimal wavelength and the range limitations of the measurement technique.
CRIS-Team Scopus Importer:2024-12-16

Optische Schaltelemente in OTDM Systemen - Schmauß, Bernhard (Conf. Proc. VDE / GMM, 2001)
UnivIS-Import:2015-04-16:Pub.2001.tech.IE.LEH.optisc

Ortsaufgeloeste Interrogation von Faser-Bragg-Gitter Sensoren mit elektro-optischer Frequenzmischung - Werzinger, Stefan; Härteis, Lisa; Köppel, Max; Schmauß, Bernhard (Workshop der ITG-Fachgruppe 5.3.1 (Modellierung photonischer Komponenten und Systeme), 2018)

OTDR Strain and Force Sensing by POF on Geotextiles in a Geotechnical Application Test - Dengler, Simon Andreas; Luber, Michael; Neff, Léon; Hangen, Hartmut; Schmauß, Bernhard; Ziemann, Olaf; Engelbrecht, Rainer (Proceedings - 28th International Conference on Optical Fiber Sensors, OFS 2023, 2023)
With polymer optical fibers (POF) attached to geotextiles, optical time domain reflectometry (OTDR) can be used to measure strain of the geotextile spatially resolved in soil. We test the technique in a geotechnical application test and thus demonstrate the functionality of the sensor for field use.
CRIS-Team Scopus Importer:2024-12-16

Outer Body Skin with an Integrated Antenna - Fuchs, Manuel; Kilian, Andreas; Brocka, Zaneta; Schmachtenberg, Ernst; Schmidt, Lorenz-Peter (Kunststoffe International, 2007)
UnivIS-Import:2015-03-09:Pub.2007.tech.IE.LEH.outerb

Output Impedance Measurement of Digitally Controlled Power Converters in LVDC-Grids - Schwanninger, Raffael; Schmitt, Daniel; Lavery, Melanie; Wunder, Bernd; März, Martin (2024 IEEE Sixth International Conference on DC Microgrids (ICDCM), 2024)
Due to the increase in possible sector couplings to local low voltage DC grids, the amount of controlled infeed converters connected to the grids increases. For these grids to remain stable, proper system analysis is required. While simulation of these systems is possible, the final setup requires measurements. In this paper, the problem of output impedance measurement of digitally controlled power converters, which make up the majority of infeed converters in medium to high power LVDC grids, is discussed. Digital control leads to several requirements regarding the test signals used to measure the converters. Due to the nonlinearity of certain power converter types, the measurements required for a full description of the power converter typically need to be taken for a variety of loads and grid voltages. Wide bandwidth measurements can be used to reduce the overall measurement time. These wide bandwidth measurements require further investigation regarding signal amplitude, which is presented in this pape

Over-the-Air Phase Noise Spectral Density Measurement for FMCW Radar Sensors - Birkenhauer, Christoph; Tschapek, Peter; Vossiek, Martin (IEEE Journal of Microwaves, 2024)
Phase noise significantly degrades the performance of frequency-modulated continuous wave (FMCW)- and chirp sequence (CS)-based radar sensors. Knowledge of the power spectral density (PSD) of these sensors is therefore essential for estimating their limitations. This work presents a test setup where over-the-air (OTA) tests can be carried out and the PSD extracted directly from the signal radiated from a radar sensor operating in the 76GHz – 81GHz automotive frequency band. For this, the radar signal is demodulated in the analog domain by mixing it with a delayed version of the received signal. Demodulation compresses the signal bandwidth, simplifying hardware requirements for sampling and signal processing. The remaining systematic errors are compensated and the range correlation effect is corrected by an appropriate signal processing scheme. Our approach eliminates the need for prior knowledge of modulation parameters, leading to both increased precision and reduced potential for errors. The proposed setup is validated comparing system measurements with data obtained from established testing methods and simulations.The presented setup successfully demonstrates the capability of performing OTA test measurements of a PSD from a FMCW sensor. Our results demonstrate good agreement between the PSD test results and the expected outcome.<br
Keywords: Phase noise; Microwave measurement; Systematics; Phase measurement; Radar measurements; Wireless networks; Radar; Sensor systems; Sensors; Noise measurement; FMCW; chirp sequence; phase noise; radar; radar sensor; phase noise measurement; automotive measurement system

Oxidized Hyaluronic Acid-Gelatin-Based Hydrogels for Tissue Engineering and Soft Tissue Mimicking - Kuth, Sonja; Karakaya, Emine; Reiter, Nina; Schmidt, Lorenz-Peter; Paulsen, Friedrich; Tessmar, Jorg; Budday, Silvia; Boccaccini, Aldo R. (Tissue Engineering - Part C: Methods, 2022)
Hydrogels are ideal materials for mimicking and engineering soft tissue. Hyaluronic acid is a linear polysaccharide native to the human extracellular matrix. In this study, we first develop and characterize two hydrogel compositions built from oxidized HA and gelatin with and without alginate-di-aldehyde (ADA) crosslinked by ionic and enzymatic agents with potential applications in soft tissue engineering and tissue mimicking structures. The stability under incubation conditions was improved by adjusting crosslinking times. Through large-strain mechanical measurements, the hydrogels' properties were compared to human brain tissue and the samples containing ADA revealed similar mechanical properties to the native tissue specimens in cyclic compression-tension. In vitro characterization demonstrated a high viability of encapsulated mouse embryonic fibroblasts and a spreading of the cells in case of ADA-free samples.
CRIS-Team WoS Importer:2022-05-20

Panel Design of a MIMO Imaging Radar at W-Band for Space Applications - Moll, Jochen; Hils, Bernd; Shrestha, Amit; Ehlert, Andre; Krozer, Viktor; Thurn, Karsten; Vossiek, Martin; Hrobak, Michael; Hossain, Maruf; Heinrich, Wolfgang; Resch, Marion; Bosse, Jurgen (14th European Radar Conference EuRAD, 2017)

Parasitic Effects in Broadband Chip Modules Based on Multilayer LTCC Technology - Nisznansky, Martin; Ziegler, Christof; Schür, Jan; Schmidt, Lorenz-Peter; Hocke, Ralf; Wohlgemuth, O. (33rd European Microwave Conference, 2003)
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.parasi

Parasitic Effects in Broadband Chip Modules Based on Multilayer LTCC Technology - Nisznansky, Martin; Ziegler, Christof; Schür, Jan; Schmidt, Lorenz-Peter; Hocke, Ralf; Wohlgemuth, Oliver (Proceedings of the 33rd European Microwave Conference, 2003)
In this paper we refer to typical parasitic and spurious effects that must be considered for the design of broadband modules. We focus on the discussion of problems like resonances and parasitic propagation modes which are typical for interconnects realized in a multilayer LTCC environment. For understanding such effects, full wave electromagnetic analysis of frequently used interconnects was performed. Then appropriate design measures were taken to avoid these undesirable effects. Further optimization steps on interconnects are described which minimize distortion of high speed digital signals. Resulting optimized interconnect structures can then be used as standard solution with guaranteed electrical performance for particular LTCC processes. Major part of the presented results were verified by measurements.

Parking space detection from a radar based target list - Prophet, Robert; Hoffmann, Marcel; Vossiek, Martin; Li, Gang (IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM 2017), 2017)
The detection of an unoccupied parking spaces is a requirement of autonomous parking systems. This paper presents a radar based real-time algorithm, which detects, classifies, and evaluates parking spaces in a vehicle's immediate vicinity. In contrast to frequently used gridmap methods, our approach processes the radar data in a specially designed target list of 2D vectors. Consequently, quantization errors are avoided and computational burdens reduced. Experiments show that the proposed algorithm is suited for both parallel and perpendicular parking spaces in urban scenes.

Particle Filter-Based SAR Approach and Trajectory Optimization for Real-Time 3D UHF-RFID Tag Localization - Gareis, Matthias; Fenske, Patrick; Carlowitz, Christian; Vossiek, Martin (2020 IEEE International Conference on RFID (RFID), 2020)
The availability of three-dimensional (3D) product maps is among the most important factors for smart warehouse environments connected to the Internet of Things. Therefore, online access to the data is a key feature that can only be provided by real-time localization systems. With the well-known synthetic aperture radar technique in combination with ultrahigh frequency (UHF) radio-frequency identification (RFID) tags, good localization results have been achieved, by labeling tags on objects and measuring the tag responses on generated trajectories, for example in warehouses, with a mobile robot platform equipped with a UHF-RFID reader. The location estimation of the tags is thus made offline after the whole synthetic aperture radar (SAR) trajectory was driven and all data are available, which can’t provide online availability of the object positions. We introduce a particle filter-based real-time localization estimation technique that involves estimating tag positions during the recording of the incoming tag signals. We first evaluate the impact of trajectories according to lateral and radial resolution and show the capability of real-time signal processing on tag counts and the amount of tag reads. We then compare our novel localization technique to the well-known grid-based approach in terms of accuracy and computational load and show the localization error improvement of our technique over the filter iteration steps by generating a 3D product map of objects labeled with standard UHF-RFID tags. The 3D root mean square error (RMSE) achieved is 2.86 cm and the computation time is reduced by a factor of more than 5

Particle Filter Based Synthetic Aperture Reconstruction Approach for Real-Time 3D Wireless Local Positioning - Li, Gang; Ebelt, Randolf; Vossiek, Martin (7th German Microwave Conference (GeMiC2012), 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 particle filtering. The synthetic aperture approach is a promising locating technique with effective multipath suppression. However, the practical usage in real-time applications is limited by its huge computational load of conventional SAR reconstruction algorithms. Instead of evaluating the PDF (probability density function) of the target position in a grid-based approach, we utilize a set of weighted particles to represent the PDF. The particle number can then subsequently be reduced in the following iterations through a resampling algorithm. It is shown by simulation and experiments with a 5.8 GHz FMCW secondary radar with 140 MHz bandwidth, that 3D localization of a robot TCP (tool center point) in mm-range with a few hundred particles is possible even in a dense multipath environment. With our new approach the computational effort has been reduced to below 0.1% compared to a grid-based evaluation. Therefore, this novel extension of particle filtering gives an attractive solution for the real-time application of 3D MISAS localization. © 2012 Institut f r Mikrowellen.
UnivIS-Import:2015-04-16:Pub.2012.tech.IE.LEH.partic
Keywords: FMCW secondary radar; indoor wireless positioning; multilateral inverse synthetic aperture secondary radar; particle filter

Passive, Wireless In Situ Millimeterwave Sensor with Mounted Dielectric Channels for Cure Monitoring of Carbon Fiber-Reinforced Polymers - Dorbath, Benedikt; Schür, Jan; Ziegmann, Gerhard; Vossiek, Martin (IEEE Sensors Journal, 2023)
Carbon fiber-reinforced polymer composites have become indispensable in certain industries, such as aeorspace, wind turbines, and automobiles, primarily due to their excellent mechanical robusteness combined with relatively low weight compared with materials of comparative strength. In addition to the choice of the matrix and fiber material within a composite, the curing process of the matrix material is essential for the final mechanical properties of the manufactured composite material. To monitor and optimize this critical curing process, we developed a passive, wireless in situ sensor that provides information about the momentary degree of cure by measuring the resonance frequency, which is dependent on the permittivity of the matrix material. This resonator-based sensor operates at around 45 GHz, which results in small geometric dimensions; its elliptical design with major axis diameters of 26 mm and 14 mm and a circuit board height of 475 μm aims to minimize the mechanical weakening of composites through the addition of the in situ sensors. Moreover, cylindrical dielectric channels mounted on top of the sensors’ orthogonally polarized patch antennas enable application of our sensor within conductive carbon fiber-reinforced polymers. The functionality of this sensor concept is confirmed with a precise simulation model and climate-controlled measurements during the curing process of epoxy resin and carbon fiber-reinforced polymers. Thereby, the measured change in resonance frequency and the predicted degree of cure of the carbon fiber-reinforced composite match closely, confirming the applicability of this sensor design in conductive carbon fiber-reinforced polymer composites.<br
Keywords: Sensors; Temperature measurement; Curing; Epoxy resins; Mechanical sensors; Permittivity measurement; Wireless sensor networks

PCB Design up to 67 GHz (W32) - PCBs for Microwave Applications up to 40 GHz and Beyond: Material Characterization, Surface Roughness Consideration, Modeling and Design Perspectives - Gold, Gerald; Helmreich, Klaus (43th European Microwave Week, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.pcbdes

PCBs for Microwave Applications up to 40 GHz and Beyond: Material Characterization, Surface Roughness Consideration, Modeling and Design Perspectives - Gold, Gerald; Helmreich, Klaus (Workshop Proceedings W32: PCB Design up to 67 GHz, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.c3scha.pcbsfo

Pedestrian Classification for 79 GHz Automotive Radar Systems - Prophet, Robert; Hoffmann, Marcel; Ossowska, Alicja; Malik, Waqas; Sturm, Christian; Vossiek, Martin (29th IEEE Intelligent Vehicles Symposium, 2018)
Radar sensors have become an integral part of advanced driver assistance systems. Merely detecting targets will not, however, advance their contribution. Rather, an object classification capability is required to distinguish vulnerable road users from other objects, such as vehicles. To achieve this, targets that are determined from the range-Doppler-Matrix created by a 79 GHz chirp sequence radar are clustered to objects. Different classifiers then use previously calculated characteristic features of moving objects to generate the object classes “Pedestrian” and “Other”. As a result, the success rate of one measurement reaches up to 95.3% for well-suited classifiers and a bandwidth of 1.6 GHz. Moreover, the robustness of the classification process is increased by tracking the objects. The proposed algorithm for pedestrian classification is not only faster than conventional approaches using micro-Doppler signatures, but also requires less computational effort. Implemented in vehicles, this can be a major contribution to protect vulnerable road users such as pedestrian
lhft_intern.bib::Prophet18c

Pedestrian Classification with a 79 GHz Automotive Radar Sensor - Prophet, Robert; Hoffmann, Marcel; Vossiek, Martin; Sturm, Christian; Ossowska, Alicja; Malik, Waqas; Lubbert, Urs (19th International Radar Symposium, 2018)
In this paper the classification of pedestrians with a 79 GHz automotive radar sensor is investigated. A suitable algorithm chain is described and tested with measurement data from various moving objects. Finally, an overview of the performance achieved with different classifiers is give

Pedestrian detection with an interlaced chirp sequence concept in automotive radar - Thurn, Karsten; Heuer, Michael; Li, Gang; Max, Stephan; Meinecke, Marc Michael; Vossiek, Martin (16th International Radar Symposium, IRS 2015, 2015)
In this paper the application of the interlaced chirp sequence (ICS) concept in pedestrian detection is examined. The ICS waveform and range-Doppler signal processing are described and the resulting system parameters are deduced. The ICS waveform exhibits good resolution and range properties and lends itself well for pedestrian detection. Measurements with a 24 GHz radar system show good result
lhft_intern.bib::Thurn2015a
Keywords: Automotive applications; frequency modulation; radar detection; radar signal processing

Performance analysis of simultaneous multilevel amplitude and phase regeneration - Röthlingshöfer, Tobias; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (39th European Conference and Exhibition on Optical Communication (ECOC), 2013)
A star-8QAM regeneration was investigated in numerical simulations for two schemes: a combined NALM with a PSA in the loop and a cascade of PSA and NALM. Significant improvements in error vector magnitude and bit error rate are achieved for both schemes in a transmission system limited by amplified spontaneous emission and nonlinear phase noise.
lhft_intern.bib::Roethlingshoefer2013a

Performance evaluation of a multi-layer reconfigurable optical-wireless network architecture employing digitized RoF - Martinez Garcia, Javier; Tsekrekos, C; Tomkos, I; Huiszoon, B (Future Network and Mobile Summit, 2011)
lhft_intern.bib::Martinez11

Performance evaluation of modulation format independent carrier phase estimation and decision directed carrier phase estimation for fiber non-linearity mitigation - Pakala, Lalitha; Schmauß, Bernhard (International Conference on Application of Photonic Technology, Photonics North, 2014)
We numerically investigate and compare the performance of modulation format independent carrier phase esti- mation (CPE) (or universal CPE (U-CPE)) and decision directed CPE (DD-CPE) along with digital backward propagation (DBP) to compensate fiber non-linearity, for polarization multiplexed (PM) 4 and 16-ary quadrature amplitude modulation (QAM) coherent systems. We analyze the impact of each of the CPE methods in reducing the complexity of DBP, in terms of required DBP steps, as well as the influence of the laser line width effects on their performance. By optimizing the step size, the U-CPE method, in spite of its low complexity, exhibits a similar performance as the DD-CPE method in non-linearity mitigation. However, at high signal launch powers, and in the presence of laser phase noise, the performance of DD-CPE method is significantly impaired owing to increased erroneous pre-decisions, whereas, the U-CPE method is still capable of mitigating both non-linearity and phase noise, equivalently good as the ideal DD-CPE case. Moreover, also without DBP for non-linear compensation, U-CPE method outperforms the DD-CPE method allowing high signal launch powers and with greater tolerance towards phase noise. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
lhft_intern.bib::Pakala2014d

Performance Evaluation of Reference Reflections in Polymer Optical Fibers for Strain Sensing - Dengler, S. A.; Gonzalez, R. V.Roseeu; Luber, M.; Ziemann, O.; Engelbrecht, R.; Schmauß, Bernhard (Optics InfoBase Conference Papers, 2022)
We present a robust concept for quasi distributed strain measurement using optical time domain reflectometry (OTDR) in polymer o pticalfibers (P OF). The spatial shifts of discrete reflective e vents in the OTDR trace are e valuated as reference points. It is shown how such reference reflections can be prepared and which properties can be expected.
CRIS-Team Scopus Importer:2024-12-16

Performance Monitoring Using Coherent Receivers - Geyer, J.C.; Fludger, C.R.S.; Duthel, T.; Schulien, C.; Schmauß, Bernhard (Optical Fiber Communication 2009, 2009)
We review performance monitoring using data of the digital equalizer of coherent receivers and show simulation and measurement results from 43Gb/s transmission data. © 2009 OSA.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.perfor
Keywords: (060.1660) Coherent communications; (060.2300) Fiber measurements

Periodic orbits for interferometric and tomographic radar imaging of Saturn’s Moon Enceladus - Benedikter, Andreas; Wickhusen, Kai; Hussmann, Hauke; Stark, Alexander; Damme, Friedrich; Rodríguez-Cassolà, Marc; Krieger, Gerhard (Acta Astronautica, 2021)
Spaceborne synthetic aperture radar interferometry and tomography are well-established techniques for the exploration of terrestrial ice sheets. In the frame of DLR’s mission concept Enceladus Explorer (EnEx), these techniques are considered for providing topography, deformation, and composition measurements, as well as 3-D metric-resolution imaging of the Enceladean ice crust. However, the formation of repeat-pass interferometric and tomographic acquisitions requires spacecraft orbits with almost perfectly repeating ground tracks and sufficient inclination for providing access to the most-interesting south polar region with its plumes. Unfortunately, the low Enceladus mass and its proximity to Saturn commonly lead to extreme instabilities for orbit inclinations beyond 60°. We show that existing orbit solutions close to this inclination barrier resulting from searches in simplified dynamic models do not exhibit sufficient stability in realistic n-body ephemeris simulations for providing the necessary repeat characteristic. We present a grid-search strategy in an ephemeris model for identifying highly-stable, periodic orbits satisfying the repeating ground track requirement. The resulting orbit solutions are assessed regarding their stability, repeat characteristic, and robustness to uncertainties in the gravitational model, navigation inaccuracies, and drag by the ejected gas and dust of the plumes. Global simulations of interferometric and tomographic acquisition geometries are used to assess the suitability of the orbits. The identified orbits provide sufficient inclination and long-term stability to sustain the required repeat characteristic up to few hundreds of days with repeat-pass baselines in the order of hundreds of meters. This may allow a consistent implementation of radar interferometric and tomographic imaging modes for a future Enceladus mission. Besides, the high stability may offer favorable conditions for other remote sensing modalities.
Keywords: Enceladus; orbit; orbit design; radar; SAR interferometry; SAR tomography

Permittivity Measurement Techniques at 24 GHz for Automative Polymer Composites Including Thin Films and Paint Foils - Kilian, Andreas; Weinzierl, Jochen; Schmidt, Lorenz-Peter (Proceedings of the German Microwave Conference, 2008)
Two different measurement techniques for the determination of complex permittivities of automotive polymer composites used as bumper or car body panels at 24 GHz are presented. The materials in focus of this research are basically plastics for injection molding like polycarbonate and its derivatives. The composites include thin dielectric films and paint foils for coloring and lamination of injection molded panels. The advantages and inconveniences of multi-layer measurements in rectangular waveguides and an open resonator are demonstrated. Additionally, an approach is proposed for further investigations on permittivity and loss tangent of automotive dielectrics in the millimeter-wave region.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.permit

Phase based multi carrier ranging for UHF RFID - Miesen, Robert; Kirsch, Fabian; Gröschel, Patrick; Vossiek, Martin (IEEE International Conference on Wireless Information Technology and Systems 2012, 2012)
The different methods to process phase measurement data of a MFCW ranging system with their characteristics are well suited to be used for UHF RFID ranging. Our measurements show that ranging ISO 18000-6C UHF RFID tags under FCC regulations is possible in outdoor conditions despite the limited bandwidth. Our next steps will be to further compare the robustness of the algorithms and to conduct measurements in multipath environments. Additionally we will combine this approach with other localization techniques. Using multiple antennas or synthetic apertures, this approach can help to increase the radial resolution significantl
lhft_intern.bib::Miesen2012a

Phase Based Tag Gate Crossing Direction Estimation - Miesen, Robert; Parr, Andreas; Vossiek, Martin (IEEE RFID 2014, 2014)
lhft_intern.bib::Miesen2014b

Phase Difference Based Precise Indoor Tracking of Common Mobile Devices Using an Iterative Holographic Extended Kalman Filter - Brückner, Stefan; Sippel, Erik; Lipka, Melanie; Geiß, Johanna; Vossiek, Martin (IEEE Open Journal of Vehicular Technology, 2022)
The 3D indoor localization of low-cost standard mobile devices represents an important research topic. Since the implementation of ultra-wideband localization systems requires elaborated hardware, a localization concept based on phase-difference-of-arrival PDOA) evaluation of narrow band communication signals at spatially distributed antennas is favorable in many applications. Typically, PDOA measurements are used to estimate the angle-of-arrival (AOA) at several receivers, which are then combined via multiangulation. However, AOA estimation requires far field conditions, thereby limiting measurement sensitivity, and distorts measurements in a non linear fashion. To overcome these limitations, this paper proposes the iterative holographic extended Kalman filter (IHEKF), which directly evaluates the phase differences between spatially distributed antenna pairs. The IHEKF requires neither a specific waveform nor emitterreceiver synchronization and, therefore, represents a good candidate for localization within communication systems such as 5G/6G. Since the evaluation of phase differences is affected by phase ambiguity, the IHEKF is designed so that closely spaced antenna pairs are evaluated first and then more distant antennas are included successively to improve accuracy. The IHEKFs capabilities are demonstrated via a 24 GHz narrow band measurement setup with strong multipath propagation, providing outstanding localization accuracy in the millimeter range without consuming any notable RF signal bandwidth.
Keywords: Location awareness; Antenna measurements; Antenna arrays; Phase measurement; Bandwith; Receiving antennas; Synchronization; Array signal processing; incoherent measurements; Kalman filter; localization; near-field; PDOA; radar

Phase-error-measurement and compensation in PLL frequency- synthesizers for FMCW sensors - I: Context and Application - Pichler, Markus; Stelzer, Andreas; Gulden, Peter; Seisenberger, Claus; Vossiek, Martin (IEEE Transactions on Circuits and Systems I-Regular Papers, 2007)
The synthesis of linear frequency sweeps or chirps is required, among others, in frequency-modulated continuous-wave radar systems for object position estimation. Low phase and frequency errors in sweeps with high bandwidth are a prerequisite for good accuracy and resolution, but, in certain applications where high measurement rates are desired, the additional demand for short sweep cycles has to be met. Transient phenomena in dynamic synthesizers as well as nonlinear system behavior usually cause unknown phase errors in the system output. For the class of phase-locked-loop (PLL)-based frequency synthesizers, a novel output phase-measurement method and dedicated circuitry are proposed that allow significant reduction of phase errors by adaptive input predistortion. The measurement procedure is implemented within the PLL control circuitry and does not require external equipment. The application of this method to PLL system identification and linearization of extremely short frequency sweeps is shown. © 2007 IEEE.
UnivIS-Import:2015-03-09:Pub.2007.tech.IE.LEH.phasee
Keywords: Chirp radar; Frequency synthesizers; Phase measurement; Phase-locked loops (PLLs)

Phase-error-measurement and compensation in PLL frequency- synthesizers for FMCW sensors - II: Theory - Pichler, Markus; Stelzer, Andreas; Gulden, Peter; Seidenberger, Claus; Vossiek, Martin (IEEE Transactions on Circuits and Systems I-Regular Papers, 2007)
Synthesizers for the generation of frequency- or phase-modulated signals are required in communications, sensing, and many other fields and applications. The widespread use of phase-locked loops (PLLs) as major building blocks in current systems requires accurate models and methods for eliminating the influence of statistical and deterministic errors in the synthesized signals. We propose a novel iterative phase-error-measurement and -compensation procedure applicable in PLL-based synthesizers, for which the mathematical background is presented, and a detailed algorithmic description is given in this work. From a mathematical PLL system model and its response to a periodic excitation by the modulating signal, a method for measuring the instantaneous output signal phase and the actual transfer function of the PLL is derived. It is shown how this knowledge can advantageously be used for pre-distorting the synthesizer input signal to eliminate deterministic errors and to obtain an accurate output phase curve. © 2007 IEEE.
UnivIS-Import:2015-03-09:Pub.2007.tech.IE.LEH.phasee_7
Keywords: Chirp radar; Frequency synthesizers; Phase measurement; Phase-locked loops (PLLs)

Phase Error Sensitivity in Multistatic Microwave Imaging Systems - Schießl, Andreas; Ahmed, S. S.; Genghammer, A.; Schmidt, Lorenz-Peter (43th European Microwave Week, 2013)
Current digital-beamforming multistatic mm-wave array designs show superior near field imaging performance. Therefore, mm-wave imaging systems based on these concepts are suitable for a variety of security, medical and industrial applications. The theoretically achieved array performance can be degraded by noise and unwanted signals within the actually implemented systems. In this work, the sensitivity of such systems on certain types of systematic errors within its signal processing chain including the system error correction mechanism is discussed and analyzed. Effects of errors within the reconstructed images are demonstrated, and methods to reduce the effects of some dominant error signals are proposed. © 2013 EMA.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.phasee
Keywords: error correction; microwave imaging; multistatic radar; signal processing

Phase Modulated 61 GHz Backscatter Transponder for FMCW Radar-Based Ranging - Stein, Wadim; Aleksieieva, Anna; Röhr, S.; Vossiek, Martin (8th German Microwave Conference (GeMiC2014), 2014)
Modulated backscatter transponders allow, low complexity, low power identification and ranging if an FMCW radar is used as a reader. Especially in industrial environments, modulation significantly increases ranging robustness by echo mitigation of passive / unmodulated reflectors. The 61 GHz ISM band is favorable for high resolution ranging due to the high available bandwidth. However, backscatter transponder design is challenging at mm-wave frequencies. In this paper, a low complexity mm-wave backscatter transponder design based on a single Schottky diode switch is introduced that allows for cost efficient manufacturing and low power consumption. A 3D full wave simulation of the proposed backscatter layout, comprising a model of the diode package, combined with its SPICE parameters in a co-simulation procedure, enables accurate circuit optimization. A complete prototype was built using planar technology that includes switch, clock generation and battery interface. Experimental results show an operating range of 20 m with a ranging uncertainty well below 25 mm at a 1 ms sweep duration of the FMCW signal. Transponder power consumption is as low as 2.5 mA with a supply voltage of 2 V.
UnivIS-Import:2015-04-16:Pub.2014.tech.IE.LEH.phasem

Phase Noise Distortion Compensation in the FMCW Radar Based on Oppositely Modulated Double Chirps - Tschapek, Peter; Fenske, Patrick; Vossiek, Martin (2024 21st European Radar Conference (EuRAD), 2024)
In coherent continuous-wave (CW) radar systems, such as frequency-modulated CW (FMCW) radar systems, phase noise significantly limits both the maximum detectable measurement range and the measurement precision for targets at long range. Approaches that minimize the amount of phase noise during signal generation have so far only led to a marginal improvement of radar systems, and are therefore unsuitable for targets over long range. This paper presents a fundamentally different approach based on full phase noise compensation, achieved by simultaneously emitting two FMCW chirps in opposite directions and then offsetting the beat frequencies. This approach was simulated and verified through measurement using an FMCW primary radar system up to the sensitivity limit of the measurement setup. The metric used was the range precision. Targets were created over ranges of 76-880 m with an analog fiber optical link. The experimental verification results showed an improvement in range precision by a factor of 43. This oppositely frequency-modulated continuous-wave (OFMCW) approach can enable high precision and low-noise measurements for future radar systems.
CRIS-Team Scopus Importer:2024-12-13
Keywords: FMCW; phase noise; phase noise compensation; phase noise modeling; radar system

Phase Noise Spectral Density Measurement of Broadband Frequency-Modulated Radar Signals - Tschapek, Peter; Körner, Georg; Hofmann, Andreas; Carlowitz, Christian; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2022)
In continuous-wave (CW) radar systems, such as frequency-modulated (FMCW), frequency-stepped (FSCW), or orthogonal frequency-division multiplexing (OFDM) radar systems, the range and velocity uncertainty are significantly impaired by phase noise decorrelation. Therefore, radar designers require accurate knowledge of their synthesizers' phase noise profiles to assess and predict radar performance. However, commercial phase noise analyzers cannot determine phase noise during modulation, and this may differ notably from phase noise in the pure CW mode. Recent methods for FMCW phase noise analysis usually require comprehensive a priori knowledge of modulation parameter and are prone to systematic deviations. To overcome these issues, we propose a new approach based on differential analysis of subsequent time-domain measurements. This method retains, statistical phase noise information while reducing systematic influences. For the first time, less a priori signal knowledge is required, and the method works for nearly any kind of broadband signal modulation. The concept requires only a digitizer (e.g., an oscilloscope) and some digital signal processing. The proposed method is first experimentally tested with different phase-locked-loop (PLL)-based synthesizer phase noise profiles. The obtained phase noise profiles agree perfectly with the results of an established measurement system. After this proof of basic functionality, the unique phase noise analysis capability for BB modulated signals is demonstrated with PLL-generated FMCW signals. The results reveal a significant phase noise difference between the different setups and clearly show the capability and benefit of the novel phase noise spectral density measurement concep
Keywords: Continuous-wave (CW) radar; frequency-modulated continuous-wave (FMCW) radar; phase locked loops; phase noise measurement; phase noise profiles

Phase-Preserving 2R-Regeneration of an 80-Gb/s RZ-DQPSK, Signal by Using a Nonlinear Amplifying Loop Mirror - Cvecek, Kristian; Sponsel, Klaus; Stephan, Christian; Ludwig, R.; Schubert, Christina; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (ECOC September, 2007)
The performance of a nonlinear amplifying loop mirror as a 2R regenerator for an 80-Gb/s RZ-DQPSK has been investigated. A significant eye-opening improvement and a negative power penalty of 2.6 dB have been obtained.
UnivIS-Import:2017-12-18:Pub.2007.tech.IE.LEH.phasep

Phase-Preserving 2R-Regeneration of a WDM RZ-DPSK Signal Using a Nonlinear Amplifying Loop Mirror - Cvecek, Kristian; Sponsel, Klaus; Stephan, C.; Onishchukov, Georgy; Ludwig, R.; Schubert, C.; Schmauß, Bernhard; Leuchs, Gerd (Optical Communication / National Fiber Optic Engineers Conference OFC/NFOEC 24.-28.02., 2008)
A modified NALM setup for phase-preserving amplitude regeneration of WDM-DPSK signals is proposed. Demultiplexing-multiplexing within the NALM fiber loop is used to avoid WDM channel crosstalk, A negative power penalty of 1.2 dB was obtained. © 2007 Optical Society of America.
UnivIS-Import:2017-11-07:Pub.2008.tech.IE.LEH.phasep

Phase preserving 2R-Regeneration using a nonlinear optical loop mirror - Cvecek, Kristian; Striegler, Arne; Meißner, Markus; Sponsel, Klaus; Schmauß, Bernhard; Leuchs, Gerd (Cleo/Europe EQEC Conference, Munich, Germany, June, 2005)
In our experiment a NOLM regenerator is adapted for reducing amplitude jitter of a DPSK signal without destroying the phase information.
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.phasep

Phase-preserving amplitude noise suppression using an attenuation-imbalanced NOLM - Parsons, E.; Stephan, K.; Sponsel, K.; Roethlingshoefer, T; Kueppers, F.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Proc. SPIE, 7621, 762109, Jan., 2010)
lhft_intern.bib::Parsons10

Phase-preserving amplitude regeneration for a WDM RZ-DPSK signal using a nonlinear amplifying loop mirror - Onishchukov, Georgy; Cvecek, Kristian; Sponsel, Klaus; Stephan, Christian; Ludwig, R.; Schubert, C.; Schmauß, Bernhard; Leuchs, Gerd (Optics Express, 2008)
We propose a modified nonlinear amplifying loop mirror (NALM) for phase-preserving 2R regeneration of wavelength division multiplexed (WDM) return-to-zero differential phase-shift-keyed signals. As proof of principle the regeneration capability of this NALM setup has been investigated experimentally for two 10 Gbit/s wavelength channels. A significant eye-opening improvement and a negative power penalty of 1.2 dB have been observed in both channels. © 2008 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.phasep

Phase-Preserving Amplitude Regeneration in DPSK Transmission Systems Using a Nonlinear Amplifying Loop Mirror - Stephan, C; Sponsel, K; Onishchukov, G; Schmauß, Bernhard (IEEE Journal of Quantum Electronics, 2009)
A phase-preserving 2R regenerator based on a nonlinear amplifying loop mirror was implemented in a RZ-DPSK transmission system. Its performance has been investigated in numerical simulations and experimentally. The results show that amplitude regeneration using a NALM can efficiently prevent accumulation of nonlinear phase noise in a 10 Gb/s DPSK transmission system. In the experiments, significant improvements of eye opening and of BER as well as a 3 dB increase in fiber launch power have been demonstrated. Simulations at 10 Gb/s and 100 Gb/s indicated that the enhancement of the transmission quality is smaller at 100 Gb/s. The reason is that at 100 Gb/s nonlinear intra-channel effects rather than pure nonlinear phase noise are the main limiting factor and the NALM can only reduce the accumulation of amplitude noise in that cas
lhft_intern.bib::stephan09

Phase-Preserving Amplitude Regeneration in DPSK Transmission Systems Using a Nonlinear Amplifying Loop Mirror - Stephan, Christian; Sponsel, Klaus; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE Journal of Quantum Electronics, 2009)
A phase-preserving 2R regenerator based on a nonlinear amplifying loop mirror was implemented in a RZ-DPSK transmission system. Its performance has been investigated in numerical simulations and experimentally. The results show that amplitude regeneration using a NALM can efficiently prevent accumulation of nonlinear phase noise in a 10 Gb/s DPSK transmission system. In the experiments, significant improvements of eye opening and of BER as well as a 3 dB increase in fiber launch power have been demonstrated. Simulations at 10 Gb/s and 100 Gb/s indicated that the enhancement of the transmission quality is smaller at 100 Gb/s. The reason is that at 100 Gb/s nonlinear intra-channel effects rather than pure nonlinear phase noise are the main limiting factor and the NALM can only reduce the accumulation of amplitude noise in that case. © 2009 IEEE.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.phasep
Keywords: 2R regeneration; Differential phase-shift keying; Nonlinear amplifying loop mirror; Nonlinear phase noise

Phase-preserving amplitude regeneration of a two-amplitude-level modulation format - Röthlingshöfer, Tobias; Richter, Thomas; Schubert, Colja; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Conference on Lasers and Electro-Optics Pacific Rim, 2013)
It has been experimentally shown that a modified nonlinear loop mirror can be used for all-optical star8-QAM processing. An amplitude noise reduction of 2.2 dB could be demonstrated for the high-power state
lhft_intern.bib::Roethlingshoefer2013b

Phase-Preserving Amplitude Regeneration Using Dispersion-Imbalanced Loop Mirror - Röthlingshöfer, Tobias; Sponsel, Klaus; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Optical Fiber Communication 2009, 2009)
Scheme and parameters of dispersion-imbalance loop mirror (DILM) have been optimized for phase-preserving amplitude 2R regeneration. DILM performance for DPSK transmission has been evaluated in numerical simulations. A 4.8 dB Q-factor improvement has been demonstrated. © 2009 OSA.
UnivIS-Import:2017-12-18:Pub.2009.tech.IE.LEH.phasep
Keywords: (060.4370) Nonlinear optics; fibers; (060.5060) Phase modulation

Phase-Preserving Multilevel Amplitude Regeneration Using a Modified Nonlinear Amplifying Loop Mirror - Hierold, M.; Roethlingshoefer, T.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (12th International Conf. on Digital Object Identifier (ICTON), Munich, June, 2010)
lhft_intern.bib::Hierold10

Phase-Preserving Signal Regeneration by a Nonlinear Amplifying Loop Mirror - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Cleo Juni, 2007)
This work presents the numerical investigations on the physical limitations and optimization of the nonlinear amplifying loop mirror (NALM) as a regenerator of phase-shift-keyed signals. The NALM consists of a bidirectional amplifier and a highly nonlinear fiber (HNLF), combined to a loop by a fiber coupler. The transfer functions for the NALM versus dispersion for an amplifier gain for anomalous and normal dispersion were studied. It should be mentioned that beside the nonlinear chirp, the NALM also causes spectral broadening and pulse shape distortions. Amplified spontaneous emission from the NALM amplifier is comparably lower and therefore negligible as a source of optical signal-to-noise ratio (OSNR) penalty.
UnivIS-Import:2017-12-18:Pub.2007.tech.IE.LEH.phasep_0

Phase regeneration of a star-8QAM signal in a phase-sensitive amplifier with conjugated pumps - Stiller, Birgit; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Optics Express, 2014)
We demonstrate numerically phase regeneration of a star-8QAM signal with two amplitude and four phase states in a phase-sensitive amplifier. In a dual-stage setup, two phase-conjugated idlers are generated in a first stage consisting of two fiber-optic parametric phase-insensitive amplifiers operated in highly nonlinear gain regime. These are used as pumps in the second, phase-sensitive amplification stage which enables efficient phase regeneration via a degenerate four-wave-mixing process. The latter can be operated in two different operation modes: without format conversion or with phase-shifted amplitude levels. In both regimes, we observe high phase-regeneration efficiency for all amplitude levels: the initial phase noise with 0.2 rad standard deviation is reduced by a factor of 5.
lhft_intern.bib::Stiller2014

Picosecond spaced pulse burst generation using a low repetition rate ultrafast fiber laser and spectral filtering - Beck, Benedikt; Kromm, Michail; Schmauß, Bernhard (Procedia CIRP, 2024)
The adaptation of laser pulse parameters is required for different material processing steps. Especially if the processing has to be done using a single laser system, a flexible variation of the pulse properties is needed. Especially the generation of pulse bursts with ps spacing enable many refinement process steps. As fiber lasers are suitable in the micro material processing regime due to their excellent beam parameter products and short pulses, an adaptive filter for pulse shaping is highly desired. This work derives a general filter theory for generating pulse bursts from ultrashort pulses and extends it for dispersion compensation. The theory is validated by simulation and experiments with a low repetition rate fiber laser and a commercial programmable optical filter. Simulations prove the viability of pulse burst generation with dispersion compensation. With the experimental setup 2-4 ps pulses with 15-25 ps spacing are generated from one ultrashort pulse.<br
Keywords: fiber laser; spectral filter; ultrafast; THz Burst; pulse shaping

Planar Bragg grating in bulk Polymethylmethacrylate - Rosenberger, M.; Koller, G.; Belle, S.; Schmauß, Bernhard; Hellmann, R. (Optics Express, 2012)
We report on a one-step writing process of a planar waveguide including a Bragg grating structure in bulk Polymethylmethacrylate (PMMA). A KrF excimer laser and a phase mask covered by an amplitude mask were used to locally increase the refractive index in PMMA and thereby generate simultaneously the planar waveguide and the Bragg grating. Our results show a reflected wavelength of the Bragg grating of about 1558.5 nm in accordance to the phase mask period. The reflectivity of the grating is about 80%. Initial characteristics of the Bragg grating structure towards humidity are investigat
lhft_intern.bib::Rosenberger2012a

Planar cross-polarized transition to a circular waveguide feed for a 61 GHz dielectric antenna - Stein, Wadim; Deckelmann, Maximilian; Oborovski, Andreas; Vossiek, Martin (9th German Microwave Conference, GeMiC 2015, 2015)
This paper presents a novel concept for a planar cross-polarized transition to a 61 GHz dielectric lens antenna. The transition to the circular waveguide antenna feed consists of a combination of a microstrip line and a slot line. Each of these planar waveguides excites the H11 mode in the circular waveguide with a 90± polarization angle to one another. The developed double layer transition topology was realized on a Rogers 5880 substrate employing the microstrip line on the top and the slot line on the bottom layer. The concept was implemented and tested on a circular waveguide-fed dielectric lens antenna for a 61 GHz radar system. Experimental results show a transition loss of around -2 dB for the microstrip and -3 dB for the slot line feed with excellent crosstalk suppression greater than 40 dB for the two polarization channels. The bandwidth of the built crosspolarized transition is greater than 10 GHz. The results prove that the novel transition concept is very well suited for compact, broadband and low cost polarimetric millimeter-wave radar systems.
Keywords: millimeter-waves; planar to waveguide transitions; polarization; slotlines

Planar D-Band Frequency Doubler and Y-Band Tripler on PTFE Laminates - Hrobak, Michael; Sterns, M.; Schramm, Marcus; Stein, Wadim; Poprawa, F.; Ziroff, A.; Schür, Jan; Schmidt, Lorenz-Peter (Proceedings of the 38th International Conference on Infrared, Millimeter and Terahertz Waves IRMMW-THz 2013, 2013)
To extend the frequency range of existing short-range radar modules for industrial applications, millimeter-wave frequency multipliers based on cost-effective PCB technology are required. This paper describes a zero-bias D-band frequency doubler and Y-band frequency tripler based on pure PTFE material and the commercially available DBES105a diode from United Monolithic Semiconductors (UMS). At an input drive level range of 16 dBm to 18 dBm the multipliers deliver output power levels POUT ∈ [5, -5] dBm from 100 GHz to 160 GHz and POUT ∈ [-11, -20] dBm from 180 GHz to 230 GHz. © 2013 IEE
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.planar

Planar integrated components perform up to 110 GHz - Menzel, W; Meinel, H; Rembold, B; Schmidt, Lorenz-Peter (Microwaves, 1982)
lhft_intern.bib::Schmidt10

Planar integrated harmonic mixers for use up to 150 GHz - Schmidt, Lorenz-Peter; Menzel, W (MIOP `87, 1987)
lhft_intern.bib::Schmidt15

Planar Varistor Mode Schottky Diode Frequency Tripler Covering 60 GHz to 110 GHz - Hrobak, Michael; Sterns, Michael; Schramm, Marcus; Stein, Wadim; Schmidt, Lorenz-Peter (Proceedings of the International Microwave Symposium 2013, 2013)
Frequency extender modules of vector network analyzers (VNA) and signal generators, as well as front end modules of semiconductor automatic testsystems (ATS) make use of broadband resistive diode frequency multipliers. We present the design and construction of a planar varistor tripler utilizing commercial gallium arsenide (GaAs) Schottky diodes on thin-film processed alumina (Al 2O3) substrate. Synthesis is based on a co-simulation procedure between 3D electromagnetic field (EM) and nonlinear circuit simulations. Measurement data over the focused output frequency range from 60 GHz to 110 GHz is presented. © 2013 IEEE.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.planar_1
Keywords: 1 mm coaxial connector; Planar W-band multiplier; Schottky diode frequency multiplier; Varistor tripler

Planar Zero Bias Schottky Diode Detector Operating in the E- and W-Band - Hrobak, Michael; Sterns, Michael; Schramm, Marcus; Stein, Wadim; Schmidt, Lorenz-Peter (Proceedings of the 43th European Microwave Week, 2013)
Schottky diode detectors are the method of choice for many scalar power measurement applications in the millimeter wave frequency range. Power monitoring of forward and backward travelling waves is especially important within signal generator frequency extension modules and front end modules of semiconductor automatic test systems (ATS). We present the synthesis and characterisation of a planar zero bias Schottky diode (ZBD) detector that covers an input frequency range of 60 GHz to 110 GHz. The planar design is based on thin-film processed Al2O3 substrate. The utilized gallium arsenide (GaAs) diodes are commercially available from Virginia Diodes, Inc. (VDI). The presented measurement data is compared to results from 3D electromagnetic field (EM) and nonlinear circuit simulations. © 2013 European Microwave Association.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.planar_5
Keywords: W-Band DC Block; W-Band Detector; W-Band RF Choke; Zero Bias Schottky Diode

Point-Cloud-Based Road Course Estimation on Automotive Radar Data - Jin, Yi; Prophet, Robert; Deligiannis, Anastasios; Fuentes-Michel, Juan-Carlos; Vossiek, Martin (2021 IEEE INTERNATIONAL CONFERENCE ON MICROWAVES, ANTENNAS, COMMUNICATIONS AND ELECTRONIC SYSTEMS (COMCAS), 2021)
CRIS-Team WoS Importer:2022-09-30

Polarimetric balanced detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing - Freitag, Stephan; Bär, Matthias; Buntzoll, Laura; Ramer, Georg; Schwaighofer, Andreas; Schmauß, Bernhard; Lendl, Bernhard (ACS Sensors, 2021)
In this work, we introduce polarimetric balanced detection as a new attenuated total reflection (ATR) infrared (IR) sensing scheme, leveraging unequal effective thicknesses achieved with laser light of different polarizations. We combined a monolithic widely tunable Vernier quantum cascade laser (QCL-XT) and a multibounce ATR IR spectroscopy setup for analysis of liquids in a process analytical setting. Polarimetric balanced detection enables simultaneous recording of background and sample spectra, significantly reducing long-term drifts. The root-mean-square noise could be improved by a factor of 10 in a long-term experiment, compared to conventional absorbance measurements obtained via the single-ended optical channel. The sensing performance of the device was further evaluated by on-site measurements of ethanol in water, leading to an improved limit of detection (LOD) achieved with polarimetric balanced detection. Sequential injection analysis was employed for automated injection of samples into a custom-built ATR flow cell mounted above a zinc sulfide multibounce ATR element. The QCL-XT posed to be suitable for mid-IR-based sensing in liquids due to its wide tunability. Polarimetric balanced detection proved to enhance the robustness and long-term stability of the sensing device, along with improving the LOD by a factor of 5. This demonstrates the potential for new polarimetric QCL-based ATR mid-IR sensing schemes for in-field measurements or process monitoring usually prone to a multitude of interferences.
CRIS-Team Scopus Importer:2021-02-12
Keywords: Attenuated total reflection; Balanced detection; Mid-infrared spectroscopy; Process analytical technology; Quantum cascade lasers

Polarimetric Decomposition Techniques for Short Range Imaging Radar - Adametz, Julian; Ullmann, Ingrid (International Microwave Symposium Workshop on Digital Signal Processing for Microwave Sensors and Imagers, 2019)

Polarimetric Radar Barcode: A Novel Chipless RFID Concept with High Data Capacity and Ultimate Tag Robustness - Pöpperl, Maximilian; Adametz, Julian; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2016)
This paper presents a novel chipless radio frequency identification (RFID) concept where the information is encoded on the tag with a 2-D polarimetric radar barcode. We achieved a data capacity with this technique that is outstanding for chipless RFID. Even though these chipless RFID tags are simple, they are extremely robust in harsh environments. The polarimetric radar barcode is formed by a set of geometric structures like small dihedral mirrors, plane surface elements, or dipole elements with different polarimetric backscattering behaviors. These structures are arranged in a 2-D array to create a specific polarimetric 2-D radar barcode. The information is read by polarimetric millimeter-wave imaging radar. The lateral resolution of the radar determines the minimum resolvable element size and is therefore critical for the maximum data capacity of the tag. We show that, theoretically, a data capacity of more than 800 bit on a surface less than the size of a credit card can be achieved if a millimeter-wave multiple-input multiple-output radar is used as reader. The polarimetric encoded reflectors can be formed by metal or reflecting ceramic structures, and the tag can consist of a single material. Thus, tag robustness is limited only by the robustness and temperature resistance of the material used. We verify the performance and functionality of the proposed chipless RFID concept with measurements taken in a laboratory test setup with a 20-bit tag and a millimeter-wave radar system with 77.5-GHz center frequency.
Keywords: Imaging; polarimetry; radar; radio frequency identification (RFID)

Polarization dependence of image fidelity in microwave mapping systems - Gniss, H; Magura, K; Karg, R; Ermert, H; Brand, Hans; Boerner, W (Institute of Electrical and Electronics Engineers, 1978)
lhft_intern.bib::thirty_years_LHFT_80

Polarization-insensitive Tunable Silicon Photonic Optical Filters for Data Center Transceivers - Alnairat, Saif; Schmauß, Bernhard; Wohlfeil, Benjamin; Djordjevic, Stevan S.; Elbers, Jörg Peter (IEEE International Conference on Group IV Photonics GFP, 2024)
We demonstrate a polarization-independent tunable silicon photonic integrated optical filter for high-speed optical transceivers. The device utilizes Polarization Splitter-Rotators (PSRs) and Vernier Microring Resonators (MRRs). The filter is configured and thermally tuned continuously across the C-band, within a feasible maximum temperature change of (70-80) K.
CRIS-Team Scopus Importer:2024-07-05
Keywords: integrated heaters; optical filters; ring resonators; silicon photonics; transceiver

Polymer planar Bragg grating for sensing applications - Rosenberger, Manuel; Hartlaub, N.; Koller, G.; Belle, S.; Schmauß, Bernhard; Hellmann, R. (SPIE Optics and Optoelectronics Conference, 2013)
Bragg gratings have become indispensable as optical sensing elements and are already used for a variety of technical applications. Mainly silica fiber Bragg gratings (FBGs) have been extensively studied over the last decades and are nowadays commercially available. Bragg grating sensors consisting of other materials like polymers, however, have only recently come into the focus of fundamental and applied research. Polymers exhibit significantly different properties advantageous for many sensing applications and therefore provide a good alternative to silica based devices. In addition, polymer materials are inexpensive, simple to handle as well as available in various forms like liquid resists or bulk material. Accordingly, polymer integrated optics attract increasing interest and can serve as a substitute for optical fibers.We report on the fabrication of a planar Bragg grating sensor in bulk Polymethylmethacrylate (PMMA). The sensor consists of an optical waveguide and a Bragg grating, both written simultaneously into a PMMA chip by a single writing step, for which a phase mask covered by an amplitude mask is placed on top of the PMMA and exposed to the UV radiation of a KrF excimer laser. Depending on the phase mask period, different Bragg gratings reflecting in the telecommunication wavelength range are fabricated and characterized. Reflection and transmission measurements show a narrow reflection band and a high reflectivity of the polymer planar Bragg grating (PPBG). After connecting to a single mode fiber, the portable PPBG based sensor was evaluated for different measurands like humidity and strain. The sensor performance was compared to already existing sensing systems. Due to the obtained results as well as the rapid and cheap fabrication of the sensor chip, the PPBG qualifies for a low cost sensing element. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onl
lhft_intern.bib::Rosenberger2013a

Polymer Planar Bragg Gratings - Rosenberger, M; Schmauß, Bernhard; Hellmann, R (Optik & Photonik, 2015)
Combining the advantageous properties of cyclo olefin copolymers (COC) with a rapid UV laser based fabrication process, we highlight the generation of planar waveguide Bragg gratings suitable for multi‐axial strain sensing (Fig. 1). Bragg gratings are optical filters reflecting a small wavelength band, which is determined by the spatial grating period and the effective refractive index. As both determining factors depend, e. g., on mechanical load conditions and temperature, measuring the reflected Bragg wavelength facilitates optical sensing of these condition
lhft_intern.bib::rosenberger2015polymer

Polymer planar Bragg grating sensor for static strain measurements - Rosenberger, Manuel; Koller, G.; Belle, S.; Schmauß, Bernhard; Hellmann, R. (Optics Letters, 2013)
We report on a new optical strain sensor based on a polymer planar Bragg grating (PPBG). The sensor consists of commercially available bulk Polymethlymethacrylate with a UV-inscribed optical waveguide as well as a Bragg grating, both of which are fabricated simultaneously in a single writing step. Upon axial strain, the Bragg wavelength reveals a quasi-instantaneous spectral red shift that depends linearly on the mechanical load with a sensitivity of 2.95 pm/με. The relative reflected intensity of the PPBG remains constant in the investigated load region. © 2013 Optical Society of Americ
UnivIS-Import:2015-03-09:Pub.2013.tech.IE.LEH.polyme

Position and Velocity Fusion Using Multiple Monostatic Radar Sensors for Automotive Applications - Schüßler, Christian; Hoffmann, Marcel; Ebelt, Randolf; Weber, Ingo; Vossiek, Martin (2021 IEEE Radar Conference (RadarConf21), 2021)
In order to protect vulnerable road users (VRU), it is essential to detect and track them reliably and to predict their direction of motion i.e., their velocity vector relative to a vehicle's driving direction. A fusion approach for monostatic radar sensors, which computes target positions and the assigned two-dimensional instantaneous velocities, is proposed to realize these functionalities. These fused detections are used to cluster extended objects. Afterwards their position, velocity, and covariance matrices are estimated. A converted measurement Kalman filter is utilized to track these detected objects. Both velocity and position can be very accurately measured with the proposed fusion algorithm. Tracking by two separated radar stations greatly outperforms a single sensor setup, as verified by test data.
Keywords: radar networks; sensor fusion; Kalman filter; automotive radar; Target tracking; Roads; Position measurement; Filtering algorithms; Radar tracking; Sensors

Position control of a robot end-effector based on synthetic aperture wireless localization - Marschall, Albert; Voigt, Thorsten; Li, Gang; Konigorski, Ulrich; Vossiek, Martin (2014 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2014, 2014)
The implementation of lightweight robot concepts requires novel measurement and control strategies to deal with the flexibility of the robot arm. To the authors' best knowledge this paper introduces for the first time an innovative closed-loop concept to measure and control the absolute position of the tool center point (TCP) based on a synthetic aperture wireless localization approach. A radio-frequency identification (RFID)-like backscatter transponder is attached to the TCP, and several radar base stations measure the respective roundtrip time-of-flight and phase of the backscattered transponder signals. Inverse radar apertures are synthesized based on a small movement of the TCP. The small TCP trajectory is tracked with simple relative sensors. A holographic synthetic aperture reconstruction algorithm then determines the absolute TCP position - i.e., the trajectory coordinates in the world coordinate system. This absolute positional information is used to observe the control system and identify model errors, which are minimized in a closed-loop procedure. This iteratively improves both the system model and control quality as well as the precision of the synthetic aperture wireless localization. System simulations and first test results prove that the novel concept is suited to measure and control the position of an end-effector with mm-precision, even if the initial system model is partly erroneous.

Positioning with Moving IEEE 802.15.4 (ZigBee) Transponders - Pichler, Markus; Schwarzer, Stefan; Stelzer, Andreas; Vossiek, Martin (IEEE MTT-S International Microwave Workshop on Wireless Sensing, Local Positioning, and RFID, 2009)
In an ever-increasing number of wireless communications applications the measurement of positions of transmitters distributed in space is desired. Demands on low cost and power consumption make solutions that allow positioning with existing communications hardware during the process of data transmission particularly interesting. In this paper we discuss a method for using IEEE 802.15.4 (ZigBee) transmitter nodes with a special frequency-hopping scheme for this purpose and show the insensitivity of this method to transmitter motion mathematically as well as by exemplary simulations and measurements. ©2009 IEEE.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.positi
Keywords: Frequency hopping; Local positioning; Sensor networks; ZigBee

Position Measurement of Multiple Microparticles in Hollow-Core Photonic Crystal Fiber by Coherent Optical Frequency Domain Reflectometry - Podschus, Jasper; Köppel, Max; Schmauß, Bernhard; Sharma, Abhinav; Sundaramahalingam, Sanju; Xie, Shangran; Russell, Philip St. J. (Optical Fiber Sensors Conference 2020 Special Edition, 2020)
Keywords: Laser beams; Laser light; Optical fibers; Optical frequency domain reflectometry; Photonic crystal fibers; Photonic crystal sensors

Possible large market applications of microwaves: Market aspectsand technological approaches (invited talk) - Schmidt, Lorenz-Peter (European Microwave Conference, 1994)
lhft_intern.bib::Schmidt30

Potential and Practical Limits of Time-Domain Reflectometry Chipless RFID - Pöpperl, Maximilian; Parr, Andreas; Mandel, Christian; Jakoby, Rolf; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2016)
This paper provides a fundamental analysis of the maximum possible information content and reading range of chipless time-domain reflectometry (TDR) radio frequency identification (RFID). Bits encoded on a tag as well as bits that can be decoded by the reader need to be considered to estimate the information content on a tag. This needs an approach that deals with the entire RFID system. Factors such as insertion loss, reader signal, reading range, and channel properties impact the number of bits that can be decoded by the reader. Taking these parameters into account on their own, we can model the signal properties at the decoder by equations from radar theory such as the Cramer-Rao lower bound. The overall performance of these systems cannot be satisfactorily described by the radar theory, as today's chipless RFID systems use different modulation schemes to increase the information content. Modulation theory can provide a detailed analysis of the modulation schemes depending on the channel and signal properties. This theory influences the tag design and the demodulation algorithms on the decoder, but is not suited to describe the RFID systems as a whole. This paper provides an approach that combines the radar and modulation theories to provide an exhaustive description of chipless TDR RFID communication. The maximum information content obtainable in practice can be estimated with this analysis. The introduced methodology is applied to surface-acoustic wave and ultra-wideband delay-line-based TDR tags. We present the simulations and measurements taken with different tags to show the practical importance of the theoretical findings.
Keywords: Chipless radio frequency identification (RFID); RFID; RFID tags

Potential of a Multimodal Orbital Radar Mission for the Exploration of Enceladus - Benedikter, Andreas; Rodriguez-Cassola, Marc; Krieger, Gerhard; Scheiber, Rolf; Martin del Campo Becerra, Gustavo; Horn, Ralf; Stelzig, Michael; Moreira, Alberto; Vossiek, Martin (EGU General Assembly 2020, 2020)
An Enceladus mission launched within a realistic time frame (e.g., launch between 2025 and 2040 and a transfer time of about ten years) would likely arrive as the sun is departing or gone from the most interesting South Polar Region marked by its active jets erupting through the ice crust. This almost drives the need for a radar instrument enabling the imaging, mapping and characterization of the moon independent of sunlight illumination. The known ice penetration capability of radar waves in the tens of MHz up to few GHz range allows for the exploration of subsurface features, whereas the surface may be imaged with high level of detail in higher frequencies up to several tens of GHz. In the frame of the Enceladus Explorer Initiative (EnEx) of the German Aerospace Center (DLR), we are currently investigating the potential of a multimodal orbital radar instrument to be used as a companion to a lander mission and to contribute in the understanding of the structure, composition and temporal variation of the Enceladean ice crust and the involved geophysical processes. The considered orbit geometries, strongly constrained by the presence of Saturn, allow for global coverage and offer half-daily revisit of the South Polar Region. We suggest a multi frequency system working concurrently in high frequency (e.g., Ka-band) and lower frequency (e.g., P-band) for surface and subsurface exploration, respectively, both capable of operating in a variety of modes: i) high resolution imaging used as a synthetic aperture radar (SAR), ii) SAR interferometer for topography, permittivity and surface and volume deformation estimates, iii) nadir looking configuration operating as an altimeter for elevation estimates and as a sounder for subsurface exploration with great penetration capability, iv) radiometer for surface temperature estimates and inversion of temperature profiles, and v) bistatic measurements between the radar instrument and an ice penetrating probe deployed by the lander with similarities to the CONSERT instrument of ESA's Rosetta mission. In this presentation, we evaluate the potential of the different modes concerning their scientific output and their usefulness for supporting the success of a lander mission. In particular the performance of SAR imaging and interferometry (single- and repeat-pass) modes are analysed, which are expected to provide key information for landing site selection such as structure, composition and topography of the surface and subsurface with metric resolution. For validation, we present results of a SAR campaign conducted using DLR's airborne sensor F-SAR over an alpine glacier, with simultaneous X- and L-band acquisitions. The campaign incorporates repeat- and single-pass acquisitions, as well as circular flights, which provide interferometric and tomographic measurements with observation geometries similar to those of an Enceladus mission. Furthermore, we provide an analysis towards a bistatic sounding experiment. Utilizing the transmission line between the radar instrument and a transponder integrated in an ice penetrating probe allows for the inversion of the spatial distribution of the dielectric ice properties and associated geophysical parameters (e.g., density, grain size, temperature, and salinity).

Präzise Prüfung von Leitungswellenwiderstand und Signalintegrität an Leiterplatten - Helmreich, Klaus (Kostengünstige Entwicklung und Fertigung komplexer Leiterplatten, 2006)
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.c3scha.przise

Precise 3-D object position tracking using FMCW radar - Vossiek, Martin; Roskosch, R.; Heide, Patric (29th European Microwave Conference, EuMC, 1999)
This paper presents a FMCW radar system for high precision three-dimensional object position tracking. Theoretical analyses of the 3-D triangulation concept and the accuracy limits are given. Three 2.45 GHz radar modules measure the distance from different spatial locations to an active reflector unit installed on the object to be localised. By modulating the radar signal in the active reflector unit, disturbing echoes and clutter noise are suppressed. An advanced signal processing concept evaluates the difference of frequency and phase terms of two adjacent modulation components. Test measurements demonstrate a 3-D position measurement with submillimetre precision. This performance makes the new approach suitable for a wide range of applications in robotics, industrial automation and in the medical area. © 1999 IEEE.
UnivIS-Import:2015-04-16:Pub.1999.tech.IE.LEH.precis

Precise and Robust crane boom tip localization using a 24 GHz radar tachymeter - Reustle, Christoph; Shmakov, Denys; Röhr, Sven; Vossiek, Martin (9th German Microwave Conference, GeMiC 2015, 2015)
This paper presents a novel radar tachymeter for safety-critical applications, using the ISM 24 GHz band for distance and angular measurements to an active target. The demonstrator system localizes the boom tip of a mobile crane during operation. This is used to determine the current working radius, in order to prevent the crane from tipping. Applying a frequency-modulated continuous-wave secondary radar concept ensures operation in the severe multipath environment typical for this type of crane. The angle of arrival is estimated using 8 receive channels in a single-input multiple-output (SIMO) configuration. Mounted at the heel section of the long telescopic boom, the tachymeter measures distance and angle with a rootmean-square error of 2.2 cm and 0.16°, respectively - showing the outstanding reliability and precision of the presented system.
Keywords: direction-of-arrival estimation; distance measurement; FMCW; position measurement; Radar applications

Precise Distance and Velocity Measurement for Real Time Locating Using a Frequency Modulated Continuous Wave Secondary Radar Approach - Röhr, Sven; Gulden, Peter; Vossiek, Martin (IEEE Transactions on Microwave Theory and Techniques, 2008)
We present a frequency-modulated continuous-wave secondary radar concept to estimate the offset in time and in frequency of two wireless units and to measure their distance relative to each other. By evaluating the Doppler frequency shift of the radar signals, the relative velocity of the mobile units is measured as well. The distance can be measured with a standard deviation as low as 1 cm. However, especially in indoor environments, the accuracy of the system can be degraded by multipath transmissions. Therefore, we show an extension of the algorithm to cope with multipath propagation. We also present the hardware setup of the measurement system. The system is tested in various environments. The results prove the excellent performance and outstanding reliability of the algorithms presented.
UnivIS-Import:2015-03-09:Pub.2008.tech.IE.LEH.precis

Precise Distance Measurement With IEEE 802.15.4 (ZigBee) Devices - Schwarzer, Stefan; Vossiek, Martin; Pichler, Markus; Stelzer, Andreas (IEEE Radio and Wireless Symposium, 2008)
In modern wireless communications products it is required to incorporate more and more different functions to comply with current market trends. A very attractive function with steadily growing market penetration is local positioning. To add this feature to low-cost mass-market devices without additional power consumption, it is desirable to use commercial communication chips and standards for localization of the wireless units. In this paper we present a concept to measure the distance between two IEEE 802.15.4 (ZigBee) compliant devices. The presented prototype hardware consists of a lowcost 2.45 GHz ZigBee chipset. For localization we use standard communication packets as transmit signals. Thus simultaneous data transmission and transponder localization is feasible. To achieve high positioning accuracy even in multipath environments, a coherent synthesis of measurements in multiple channels and a special signal phase evaluation concept is applied. With this technique the full available ISM bandwidth of 80MHz is utilized. In first measurements with two different frequency references-a low-cost oscillator and a temperatur- compensated crystal oscillator-a positioning bias error of below 16 cm and 9 cm was obtained. The standard deviation was less than 3 cm and 1 cm, respectively. It is demonstrated that compared to signal correlation in time, the phase processing technique yields an accuracy improvement of roughly an order of magnitude. © 2008 IEEE.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.precis_3

Precise local-positioning for autonomous situation awareness in the Internet of Things - Kirsch, Fabian; Miesen, Robert; Vossiek, Martin (2014 IEEE MTT-S International Microwave Symposium, IMS 2014, 2014)
This paper reviews different wireless local positioning principles and explains the interaction between local positioning and the Internet of Things (IOT). The principle, performance and use of recent local positioning systems in the context of the IOT are shown in detail for typical applications. The first application is the accurate real-time localization of transportation vehicles using local positioning radar. The second application is the loading state characterization of goods in the proximity of a forklift enabling fully automated warehouse management. The third application is the dynamic localization of UHF-RFID tags with a handheld reader, which provides helpful augmented reality for logistics personnel. The final application is the real-time localization of tools for production monitoring. The developed ultrawideband (UWB) locating system is based on a pulsed frequency modulated continuous wave (FMCW) radar principle. By using assisting inertial sensors and advanced fusion algorithms, highly accurate 3D localization was achieved even in complex industrial environments with dense multipath channels and shadowing. © 2014 IEEE.
Keywords: FMCW; internet of things; position measurement; radar applications; radar tracking; RFID tags; transponder; wireless sensor networks

Precise ranging and simultaneous high speed data transfer using mm-wave regenerative active backscatter tags - Carlowitz, Christian; Vossiek, Martin; Strobel, Axel; Ellinger, Frank (IEEE RFID 2013, 2013)
For precise ranging in dense indoor RFID applications, a large absolute bandwidth is required for effective multipath suppression. Since the bandwidth of UHF systems is severely restricted, we propose mm-wave tags combined with high volume data storage and high speed data transfer (≫10 MBit/s) as an attractive alternative - in short range (1-10 m) augmented reality and multimedia applications, for example. A regenerative active backscatter tag based on a pulsed injection-locked oscillator is suggested in order to achieve a sufficiently high reader SNR for high bandwidth communication. This paper demonstrates that a 34.3-34.8 GHz frequency modulated continuous wave (FMCW) RFID ranging approach can be integrated seamlessly with simultaneous data transmission from the modulated active backscatter tag to the reader at 37.5 MBit/s. Mutual distortions between FMCW ranging and data transmission are prevented by line encoding and quadrature mixing. © 2013 IEE
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.precis
Keywords: injection-locked oscillators; millimeter wave communication; millimeter wave radar; radio frequency identification; signal sampling

Predictive NLOS Detection for UWB Indoor Positioning Systems Based on the CIR - Schröer, Guido; Haefner, Bernhard (2018 15TH WORKSHOP ON POSITIONING, NAVIGATION AND COMMUNICATIONS (WPNC), 2018)
CRIS-Team WoS Importer:2019-03-20

Printed Circuit Board Material Characterization at Millikelvin Temperatures for Cryogenic Microwave Circuit Design - Zocher, Nicole; Pfahler, Tim; Vossiek, Martin; Carlowitz, Christian (2024 54th European Microwave Conference (EuMC), 2024)
Cryogenic microstrip designs are required for integration in quantum computers. However, precise substrate characterization is necessary for more complex microwave circuit design but has not been throughly performed in the millikelvin (mK) range. This work presents a cryogenic calibration-free method for the characterization of printed circuit board (PCB) materials for microwave circuit design in cryogenic environments. The relative permittivity and the attenuation coefficient were determined using microstrip lines (MSLs) and ring resonators down to 40 mK. It is shown that at 40 mK the relative permittivity of the common and widely available Rogers RO4350B RF substrate only changes by 1 % and that the attenuation coefficient at 40 mK is reduced by 42 % compared to room temperature, proving its suitability for microwave PCB design for mK temperature

Prinzip und Aufbau moderner CO_2-Laser oder die Renaissance eines Arbeitspferdes - Engelbrecht, Rainer (Bayerische Laserseminare: Gaslaser - Auslaufmodelle oder Dauerbrenner, März, 2004)
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.prinzi

Prinzip und Grenzen von Leistungslasern - Brand, Hans (1988)
lhft_intern.bib::thirty_years_LHFT_242

Program FFlexCom - High frequency flexible bendable electronics for wireless communication systems - Meister, Tilo; Ellinger, Frank; Bartha, Johann W.; Berroth, Manfred; Burghartz, Joachim; Claus, Martin; Frey, Lothar; Gagliardi, Alessio; Grundmann, Marius; Hesselbarth, Jan; Klauk, Hagen; Leo, Karl; et al. (2017 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS), 2017)
Keywords: flexible electronics; radiocommunication; DFG Priority Program FFlexCom; flexible bendable electronics; wireless communication systems; Integrated circuit modeling; Metals; Microwave antennas; Substrates; Thin film transistors; Wireless communication

Program FFlexCom — High frequency flexible bendable electronics for wireless communication systems - Vossiek, Martin (IEEE International Conference on Microwaves, Communications, Antennas and Electronic Systems, 2017)
Today, electronics are implemented on rigid substrates. However, many objects in daily-life are not rigid - they are bendable, stretchable and even foldable. Examples are paper, tapes, our body, our skin and textiles. Until today there is a big gap between electronics and bendable daily-life items. Concerning this matter, the DFG Priority Program FFlexCom aims at paving the way for a novel research area: Wireless communication systems fully integrated on an ultra-thin, bendable and flexible piece of plastic or paper. The Program encompasses 13 projects led by 25 professors. By flexibility we refer to mechanical flexibility, which can come in flavors of bendability, foldability and, stretchability. In the last years the speed of flexible devices has massively been improved. However, to enable functional flexible systems and operation frequencies up to the sub-GHz range, the speed of flexible devices must still be increased by several orders of magnitude requiring novel system and circuit architectures, component concepts, technologies and material

Progress in Digital Backward Propagation (invited) - Schmauß, Bernhard; Lin, Chien-Yu; Asif, Rameez (38th European Conference and Exhibition on Optical Communication (ECOC), 2012)
Digital backward propagation (DBP) as a method to compensate signal distortions caused by group velocity dispersion and Kerr nonlinearity attracts much attention. As an inverted propagation simulation of the received signal is the key element of DBP, the main challenges is to reduce the computational effort. We review methods developed so far.
lhft_intern.bib::Schmauss2012cb

Promotion von FH-Absolventen - ja, wieso nicht? Mitteilungen des Hochschulverbandes, Jg - Brand, Hans (1991)
lhft_intern.bib::thirty_years_LHFT_282

Propagation Parameter Tracking using Extended Kalman Filter - Pakala, Lalitha (Friedrich-Alexander-Universität Erlangen-Nürnberg, 2011)

Prozessabhängigkeit der dielektrischen Eigenschaften im FFF von COC - Romeis, Manuel; Ehrngruber, Michael; Drummer, Dietmar (Tagungsband Technomer:, 2023)
Das rasante Fortschreiten der technologischen Entwicklungen in Richtung Internet der Dinge erfordert den Austausch immer größerer Datenmengen, wodurch die Anforderungen an entsprechende Antennensysteme ebenfalls weiter wächst. Durch die komplexe Formgebung und die Eröffnung komplett neuer Geometriemöglichkeiten bieten sich Additive Fertigungsverfahren für die Herstellung solch innovativer Systeme natürlicherweise an. Eine Kombination aus einem Kunststoffgrundkörper und einer Metallisierung bietet hier eine Vielzahl von dielektrischen Eigenschaften und damit Anwendungsfeldern. Ein neuartiger Ansatz bevorzugt eine Außenmetallisierung gegenüber der klassischerweise eingesetzten Innenmetallisierung, um so die Geometrievielfalt nicht durch eine benötigte Zugänglichkeit der Innenstrukturen einzuschränken und so in innovativen und neuen Designs zu denken. Da allerdings in diesem Fall das elektromagnetische Feld durch den Kunststoff geleitet wird, müssen für diesen Prozess sehr verlustarme Kunststoffe für additive Fertigungsverfahren qualifiziert werden. Ein Kunststoff mit ausgezeichneten Voraussetzungen zur Erreichung dieser Zieleigenschaften ist COC. Eingesetzt wird im Rahmen dieser Untersuchung ein kommerzielles COC Filament der Firma CREAMELT und die Verarbeitung findet auf einer OpenSource FFF-Anlage der Firma Prusa statt. Im Rahmen der gezeigten Untersuchung findet eine Evaluierung der Prozess-Bauteileigenschafts-Zusammenhänge statt. Parameter, die dabei variiert werden, sind Verarbeitungstemperatur, Schichtdicke sowie Düsendurchmesser. Speziell die Variation des Düsendurchmessers ist hierbei ein wichtiger Aspekt um in die Abmessungen der angestrebten Antennenanwendung zu gelangen. Die Ergebnisse, die hierbei charakterisiert werden ist der Einfluss auf die Bauteilabmessungen, Oberflächenrauheit, Dichte sowie die dielektrischen Eigenschaften im Bereich 20 – 50 GHz mit Hilfe eines speziell für diesen Zweck angefertigten Messresonators. Ziel ist es daraus Fertigungsrichtlinien zur Erreichung der gewünschten Eigenschaften zu erstellen.Mit reduzierter Schichthöhe und Erhöhung der Temperatur findet eine bessere Einhaltung der Sollmaße statt. Die Änderung des Düsendurchmessers zeigt keinen Einfluss in der Untersuchung der Abmessungen, allerdings eine deutliche Verbesserung der Oberflächenqualität, die Dichte wiederum fällt mit der Reduktion des Düsendurchmessers geringer aus. Ein Einfluss der Schichthöhe konnte hier nicht gezeigt werden. Bei den Messungen der dielektrischen Eigenschaften konnte eine Reduktion der relativen Permittivität sowohl mit der Erhöhung des Düsendurchmessers sowie einer Erhöhung der Temperatur und Schichtdicke gezeigt werden. Der dielektrische Verlust zeigt ebenfalls eine Reduktion mit Zunahme des Düsendurchmessers. Ein Einfluss der Temperatur sowie der Schichthöhe konnte in den Untersuchungen nicht gezeigt werden. Durch eine Bewertung von dem Zusammenspiel aus Bauteilqualität und dielektrischen Eigenschaften können so optimierte Parameter für die Fertigung von Antennenarrays abgeleitet werde

PSK Modulator for Regenerative Sampling Gigabit UWB Communication - Carlowitz, Christian; Vossiek, Martin (8th German Microwave Conference (GeMiC2014), 2014)
To achieve high data rates in ultra-wideband communication systems, complex pulse modulation schemes like high order phase shift keying (PSK) are required in order to increase spectral efficiency. In this work, a synthesizer concept based on a passive switched-line phase modulator is introduced where both the modulation control and the RF carrier signal are provided by standard digital drivers. A high switching speed of 400 MHz at 6 GHz carrier frequency is achieved using Schottky diode switches to deliver a 1.2 GBit/s throughput using a 3-bit modulator (8-PSK). The switched injection-locked oscillator ¿ as the only active RF element for pulse generation with phase regeneration from a weak injected signal ¿ allows for both high insertion losses (11 dB) at the phase modulator as well as RF carrier generation from a low power harmonic of a baseband signal. The result is a PSK UWB transmitter with low power consumption and low system complexity, without any need for RF PLL, linear amplifiers, DACs or an analog baseband.
UnivIS-Import:2015-04-16:Pub.2014.tech.IE.LEH.pskmod

Pulsed Frequency Modulation Techniques for High-Precision Ultra Wideband Ranging and Positioning - Waldmann, Benjamin; Gulden, Peter; Vossiek, Martin; Weigel, Robert (IEEE International Conference on Ultra-Wideband, ICUWB 2008, 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. The system combines the advantages of FMCW radar systems and the advantages of the use of a wide bandwidth. With this concept, a high accuracy in dense multipath indoor environments can be achieved, ideally suited for ID, 2D, and 3D localization. A prototype was fabricated which operates around 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.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.pulsed

Qualifizierter Ingenieurnachwuchs - Anforderungen an das Bildungssystem - Brand, Hans (ETZ. Elektrotechnische Zeitschrift Berlin, 1982)
lhft_intern.bib::thirty_years_LHFT_137

Quasi-Coherent Phase-Based Localization and Tracking of Incoherently Transmitting Radio Beacons - Sippel, Erik; Hehn, Markus; Kögel, Tobias; Gröschel, Patrick; Hofmann, Andreas; Brückner, Stefan; Geiß, Johanna; Schober, Robert; Vossiek, Martin (IEEE Access, 2021)
The direct measurement of distance-dependent information between wireless units represents a challenge for wireless locating systems, because it requires the exact time synchronization of separate wireless units. To avoid these synchronization efforts, many wireless locating systems only evaluate phase difference of arrival (PDOA) measurements. While simple PDOA localization techniques rely on multiangulation, advanced PDOA concepts like the holographic extended Kalman filter (HEKF) directly evaluate the measured phases without non-linear preprocessing. However, these differential phase measurement approaches are less sensitive than systems that can measure absolute phase variations, which allow the tracking of much smaller position changes than the signal’s carrier wavelength. This paper proposes to extend the HEKF by the evaluation of absolute phases in an incoherent measurement setup, which consists of a continuous wave (CW) beacon and several receivers. The developed quasi-coherent holographic extended Kalman filter (QCHEKF) uses the overdetermined PDOA measurements to estimate the phase–frequency relation between each beacon–receiver pair. Then, the established phase–frequency relations allow the evaluation of absolute phase measurements and, thus, the accurate localization and tracking of a simple, unsynchronized, narrowband CW beacon, even under severe multipath conditions. This novel concept is experimentally validated via 3D localization results in a challenging indoor scenario using a 24 GHz CW measurement setup. Here, the QCHEKF improves the achieved localization accuracy in comparison to the HEKF by 35% from 0.78 cm to 0.51 cm, while the maximum deviation from the trajectory reduces by 68% from 5 cm to 1.6 cm. Furthermore, the QCHEKF enables the exact tracking of fast changes in direction, which is usually a significant challenge for standard wireless target tracking systems.
Keywords: Phase measurement; Location awareness; Antenna measurements; Time-frequency analysis; Receiving antennas; Time measurement; Wireless sensor networks

Quasi-Distributed Fiber Bragg Grating Sensing Using Stepped Incoherent Optical Frequency Domain Reflectometry - Werzinger, Stefan; Bergdolt, Sven; Engelbrecht, Rainer; Thiel, Torsten; Schmauß, Bernhard (Journal of Lightwave Technology, 2016)
We examine the quasi-distributed interrogation of fiber Bragg grating arrays (FBGA) with the method of stepped incoherent optical frequency domain reflectometry (IOFDR) combined with wavelength scanning of a tunable laser source. The technique of IOFDR provides some advantages over traditional time division multiplexing schemes, because continuous wave modulation of the light intensity instead of short and low energy pulses is used, maximizing the reflected signal received from the sensor fiber. Moreover, an electrical heterodyne demodulation by a microwave vector network analyzer provides a low-noise detection, while achieving high spatial resolutions down to the centimeter range. A quasi-distributed temperature measurement with ten FBGs of 0.5% reflectivity is demonstrated. In the experiment, a root mean square temperature error of 0.3 K and a maximum error of 1 K is observed, using a fiber-coupled power of only -12 dBm. A spatial two-point resolution of 2.14 cm is achieved, which enabled a successful interrogation of FBGAs with 20 and 30 cm spacings. The potential multiplexing capability of the given setup could reach more than 50 gratings in a 30 cm spacing at a measurement rate of 50 s/n
lhft_intern.bib::Werzinger2016c

Quasi-distributed temperature sensing with large-scale draw tower gratings - Härteis, Lisa-Sophie; Renner, Esther; Scheffter, Kilian; Schmauß, Bernhard (Optics InfoBase Conference Papers, 2021)
Large-scale draw tower gratings (DTG) are interrogated using incoherent optical frequency domain reflectometry (iOFDR) w ith h omodyne f requency conversion. We successfully demonstrate quasi-distributed temperature sensing with a total number of N = 500 DTGs.
CRIS-Team Scopus Importer:2021-12-17

Quasi-Optical Directional Coupler Based on 3D-Printed Dielectric Image Lines for sub-THz Applications - Hahn, Leonhard; Bürk, Lukas; Zhu, Yu; Carlowitz, Christian; Gold, Gerald; Ellinger, Frank; Vossiek, Martin (2024 54th European Microwave Conference (EuMC), 2024)
This paper presents a 3D-printed dielectric directional coupler for the sub-THz band from 140GHz to 220GHz. In contrast to conventional coupling approaches, a quasi-optical operating principle is implemented, which is based on the insertion of a thin dielectric boundary within a dielectric image guide. Due to an intended permittivity shift, the boundary layer acts as a wavesplitter for incident HE11 waves, whose partial reflections are selectively controllable via material or geometry parameters. This results in significant advantages in terms of achievable bandwidth and required dimensions, while manufacturing costs and complexity are minimized at the same time using additive manufacturing. The realized coupler exhibits broadband matching of approx. 20dB, with high isolation of 25dB and achieves freely configurable, reproducible broadband coupling attenuation between 5dB and 15dB. Due to the remarkable simplicity and small size of the concept, this demonstrates a promising key component for low-loss, large-scale, dielectric sub-THz signal distribution networks.
CRIS-Team Scopus Importer:2024-12-13
Keywords: Couplings; Distribution networks; Three-dimensional printing; Reflection; Dielectrics; Broadband communication; Manufacturing; Permittivity; Directional couplers; Microwave imaging; Dielectric image lines; directional coupler; 3D-printing; quasi-optical; sub-THz

Quasiplanar 3 dB hybrid for millimetre-wave integrated circuits - Callsen, H; Schmidt, Lorenz-Peter (Electronics Letters, 1982)
lhft_intern.bib::Schmidt12

Radar and Lidar Deep Fusion: Providing Doppler Contexts to Time-of-Flight Lidar - Jin, Yi; Kuang, Yongshao; Hoffmann, Marcel; Schüßler, Christian; Deligiannis, Anastasios; Fuentes-Michel, Juan-Carlos; Vossiek, Martin (IEEE Sensors Journal, 2023)
This work proposes a novel sensor fusion-based, single-frame, multiclass object detection method for road users, including vehicles, pedestrians, and cyclists, in which a deep fusion occurs between the lidar point cloud (PC) and the corresponding Doppler contexts, namely, the Doppler features, from the radar cube. Based on convolutional neural networks (CNNs), the method consists of two stages: In the first stage, region proposals are generated from the voxelized lidar PC, and relying on these proposals, Doppler contexts are cropped from the radar cube. In the second stage, using fused features from the lidar and radar, the method achieves object detection and object motion status classification tasks. When evaluated with measurements in inclement conditions, which are generated by a foggification model from real-life measurements, in terms of the intersection over union (IoU) metric, the proposed method outperforms the lidar-based network by a large margin for vulnerable road users, namely, 4.5% and 6.1% improvement for pedestrians and cyclists, respectively. In addition, it achieves 87% F1 score (81.6% precision and 93.1% recall) for single-frame, object motion status classificatio
CRIS-Team Scopus Importer:2023-11-10
Keywords: Convolutional neural network (CNN); deep learning; object detection; sensor fusion

Radar-Based Continuous Human Activity Recognition with Multi-Label Classification - Ullmann, Ingrid; Guendel, Ronny G.; Kruse, Nicolas Christian; Fioranelli, Francesco; Yarovoy, Alexander (IEEE SENSORS, 2023)
This paper presents a novel approach to radar-based human activity recognition in continuous data streams. To date, most work in this research area has aimed at either classifying every single time step separately by means of recurrent neural networks, or using a two-step procedure of first segmenting the stream into single activities and then classifying the segment. The first approach is restricted to time-dependent data as input; the second approach depends crucially on the segmentation step. To overcome these issues we propose a new approach in which we first segment the stream into windows of fixed length and subsequently classify each segment. Since due to the fixed length, the segment is not restricted to one activity alone, we use a multi-label classification approach, which can account for multiple activities taking place in the same segment by giving multiple outputs. To obtain a higher classification accuracy we fuse several radar data representations, namely range-time, range-Doppler and spectrogram. Using a publicly available dataset, an overall classification accuracy of 95.8% and F1 score of 92.08% could be achieved with the proposed metho
Keywords: continuous human activity recognition; radar; multi-label classification; deep learning; ResNet; activities of daily living

Radar-Based High-Accuracy 3D Localization of UAVs for Landing in GNSS-Denied Environments - Dobrev, Yassen; Dobrev, Yavor; Gulden, Peter; Lipka, Melanie; Pavlenko, Tatiana; Moormann, Dieter; Vossiek, Martin (IEEE MTT-S Int. Conf. on Microwaves for Intelligent Mobility (ICMIM 2018), 2018)

Radar based localisation of tools in production szenarios - Kirsch, Fabian; Vossiek, Martin (Workshop on "Microwave Sensors & Sensor Systems," 6th German Microwave Conference (GeMiC) 2011, 2011)
lhft_intern.bib::Kirsch2011

Radar-based Recognition of Activities of Daily Living in the Palliative Care Context Using Deep Learning - Bräunig, Johanna; Mejdani, Desar; Krauß, Daniel; Grießhammer, Stefan; Richer, Robert; Schüßler, Christian; Yip, Julia; Steigleder, Tobias; Ostgathe, Christoph; Eskofier, Björn; Vossiek, Martin (2023 IEEE EMBS International Conference on Biomedical and Health Informatics (BHI), 2023)
The accurate detection and quantification of activities of daily life (ADL) are crucial for assessing the health status of palliative patients to allow an optimized treatment in the last phase of life. Current evaluation methods heavily rely on subjective self-reports or external observations by clinical staff, lacking objectivity. To address this limitation, we propose a radar-based approach for recognizing ADLs in a palliative care context. In our proof of concept study, we recorded five different ADLs relevant to palliative care, all occurring within a hospital bed, from N=14 healthy participants (57% women, aged 28.6 ± 5.3years). All movements were recorded using two frequency-modulated continuous wave radar systems measuring velocity, range, and angle. A convolutional neural network combined with long short-term memory achieved a classification accuracy of 99.8 ± 0.4% across five cross-validation folds. Furthermore, we compare our initial approach, which takes into account all dimensions of the available radar data, to a simplified version, where only velocity information over time is fed into the network. While these results demonstrate the high potential of radar-based sensing to automatically detect and quantify activities in a palliative care context, future work is still necessary to assess the applicability to real-world hospital scenarios.<br
Keywords: Hospitals; Radar measurements; Pipelines; Neural networks; Radar; Particle measurements; Frequency measurement

Radar-Based Recognition of Static Hand Gestures in American Sign Language - Schüßler, Christian; Zhang, Wenxuan; Bräunig, Johanna; Hoffmann, Marcel; Stelzig, Michael; Vossiek, Martin (2024 IEEE Radar Conference, 2024)
In the fast-paced field of human-computer interaction (HCI) and virtual reality (VR), automatic gesture recognition has become increasingly essential. This is particularly true for the recognition of hand signs, providing an intuitive way to effortlessly navigate and control VR and HCI applications. Considering increased privacy requirements, radar sensors emerge as a compelling alternative to cameras. They operate effectively in low-light conditions without capturing identifiable human details, thanks to their lower resolution and distinct wavelength compared to visible light. While previous works predominantly deploy radar sensors for dynamic hand gesture recognition based on Doppler information, our approach prioritizes classification using an imaging radar that operates on spatial information, e.g. image-like data. However, generating large training datasets required for neural networks (NN) is a time-consuming and challenging process, often falling short of covering all potential scenarios. Acknowledging these challenges, this study explores the efficacy of synthetic data generated by an advanced radar ray-tracing simulator. This simulator employs an intuitive material model that can be adjusted to introduce data diversity. Despite exclusively training the NN on synthetic data, it demonstrates promising performance when put to the test with real measurement data. This emphasizes the practicality of our methodology in overcoming data scarcity challenges and advancing the field of automatic gesture recognition in VR and HCI application
Keywords: Hand Gesture Recognition; Microwave Imaging; Machine Learning; Radar Simulation; Ray Tracing

Radar-Based Tremor Quantification Using Deep Learning for Improved Parkinson’s and Palliative Care Assessment - Mejdani, Desar; Bräunig, Johanna; Grießhammer, Stefan; Krauß, Daniel; Steigleder, Tobias; Engel, Lukas; Jukic, Jelena; Rozhdestvenskaya, Anna; Winkler, Jürgen; Eskofier, Björn; Ostgathe, Christoph; Vossiek, Martin (IEEE Transactions on Radar Systems, 2024)
Tremor is one of the most prevalent movement disorders, which is especially observed in patients with Parkinson’s disease (PD) and other conditions common in palliative care (PC). Effective treatment and monitoring of disease progression are crucial in the context of PC for patients suffering from movement disorders. To this aim, accurate and continuous detection and assessment of tremor characteristics, such as the tremor frequency, is required. Current evaluations by clinicians conducted during sporadic consultations are subjective and intermittent. Radar sensors provide continuous, objective evaluations of tremor motion in patient monitoring, offering a contactless, light-independent, and privacy-preserving method that directly measures tremor’s radial motion through the Doppler effect. As previous radar-based research lacks continuous tremor monitoring in realistic scenarios, this study uses a frequency-modulated continuous-wave (FMCW) radar to detect subtle tremor motions and estimates their frequencies amid challenges such as large body motion interference in a clinical setting. Seventeen healthy participants were instructed to mimic tremors in their right hand while performing three diagnostics movements frequently used in tremor assessment, and two activities that were inspired by common daily tasks encountered in PC settings. Tremor detection and frequency estimation was enabled using suitable radar signal preprocessing followed by a neural network comprising convolutional and recurrent layers. Reference frequencies were obtained from an inertial measurement unit (IMU) attached to the participants’ right hands. Cross-validation revealed a mean absolute error (MAE) of 1.47 Hz in radar-based frequency estimation compared with the reference and a 90% accuracy in distinguishing the presence or absence of tremor, highlighting the proposed approach’s high potential for future tremor assessmen
Keywords: Sensors; Radar antennas; Palliative care; Frequency estimation; Doppler effect; Chirp; Kinetic theory; Doppler radar; Deep learning; Parkinson's disease; Deep learning; neural network; palliative care (PC); Parkinson’s disease (PD); radar; tremor

Radar Interferometry and Tomography for the Exploration of Enceladus' Surface and Subsurface: Feasibility and Potential - Benedikter, Andreas; Wickhusen, Kai; Hussmann, Hauke; Stark, Alexander; Rodriguez-Cassola, Marc; Krieger, Gerhard; Damme, Friedrich (AGU Fall Meeting, 2021)

Radar in the Rain: Understanding and Simulating Environmental Effects on ADAS Radar Sensors - Wachtel, Diogo; Rothmeier, Thomas; Von Dem Bussche, Tetmar; Huber, Werner; Vossiek, Martin (Proceedings of the IEEE Radar Conference, 2024)
Advanced driver assistance systems (ADAS) depend heavily on clear and precise environmental perception. It is a known issue that vision-based sensors, like cameras and LIDARs, may experience a significant performance decline in adverse weather conditions, such as heavy rain and thick fog. Radar sensors, operating in different frequency ranges, offer a partial solution by overcoming some limitations associated with vision-based environmental perception. Simulation has become an invaluable tool for validating driving functions and sensors within a virtual environment, offering the capability to replicate critical scenarios and systematically adjust weather conditions for testing. Nonetheless, the reliability of the simulation tool must be verified through validation against real-world scenarios. The effect of raindrops over the radar rays should be studied to understand the possible impact on environmental perception. This work analyses two radar sensors' measured radar cross section (RCS) under several rain conditions and proposes a model to simulate the rain effects on the radar rays. The results revealed that not only does the rain intensity play a role in the radar detection, but the asphalt condition, whether dry or wet, increases the multipath effect, reducing the accuracy of the radars. The proposed model confirms the possibility of simulating the power-loss impact by matching the limits of real measurements.
CRIS-Team Scopus Importer:2024-07-05
Keywords: FMCW Radar; Weather Conditions

Radar Target Simulator Based on Instantaneous Intra-Chirp FMCW Parameter Estimation - Birkenhauer, Christoph; Körner, Georg; Stief, Patrick; Gareis, Matthias; Carlowitz, Christian; Vossiek, Martin; Birkenhauer, Christoph; Kuhnlein, Matthias; Korner, Georg; Stief, Patrick; Gareis, Matthias; Carlowitz, Christian; et al. (20th European Radar Conference, EuRAD 2023, 2023)
Keywords: radar target simulation; automotive radar; parameter estimation; FMCW

Radar Travel Time Tomography for Subsurface Ice Exploration at Saturn's Moon Enceladus - Huber, Christian; Benedikter, Andreas; Krieger, Gerhard; Rodriguez-Cassola, Marc (2021 18TH EUROPEAN RADAR CONFERENCE (EURAD), 2022)
We present an iterative travel time inversion approach for mapping the subsurface permittivity distribution within the ice crust of Saturn's moon Enceladus utilizing bistatic transmission lines between an orbital radar and an active target (transponder) located in the ice. The approach builds on the dependence between the measured radar travel times and the underlying permittivity distribution. The estimated permittivity distribution can then be used to infer physical parameters of the Enceladus ice crust such as density, temperature, and grain size. Building on the same rationale, we furthermore suggest an effective localization strategy for targets located in the ice crust. Both permittivity distribution estimate and localization show promising results when tested on synthetic dat
CRIS-Team WoS Importer:2022-08-26

Radio Frequency Modeling of Receive Coil Arrays for Magnetic Resonance Imaging - Stumpf, Christopher; Malzacher, Matthias; Schmidt, Lorenz-Peter (2018)
The numerical calculation of the signal-to-noise ratio (SNR) of magnetic resonance imaging (MRI) coil arrays is a powerful tool in the development of new coil arrays. The proposed method describes a complete model that allows the calculation of the absolute SNR values of arbitrary coil arrays, including receiver chain components. A new method for the SNR calculation of radio frequency receive coil arrays for MRI is presented, making use of their magnetic B1−" role="presentation">B−1 transmit pattern and the S-parameters of the network. The S-parameters and B1−" role="presentation">B−1 fields are extracted from an electromagnetic field solver and are post-processed using our developed model to provide absolute SNR values. The model includes a theory for describing the noise of all components in the receiver chain and the noise figure of a pre-amplifier by a simple passive two-port network. To validate the model, two- and four-element receive coil arrays are investigated. The SNR of the examined arrays is calculated and compared to measurement results using imaging of a saline water phantom in a 3 T" role="presentation">3 T scanner. The predicted values of the model are in good agreement with the measured values. The proposed method can be used to predict the absolute SNR for any receive coil array by calculating the transmit B1−" role="presentation">B−1 pattern and the S-parameters of the network. Knowledge of the components of the receiver chain including pre-amplifiers leads to satisfactory results compared to measured values, which proves the method to be a useful tool in the development process of MRI receive coil arrays.
Keywords: receive coil array; SNR modeling; MRI; pre-amplifier noise; noise coupling

Radiofrequente Ortung für Verkehr & Logistik - Vossiek, Martin (Workshop "RFID in Verkehr & Logistik, 2006)
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.radiof

Radiofrequente Ortung von Fahrzeugen in der Produktion und Logistik - Vossiek, Martin (13. Niedersächsische Telekolloquium zum Thema "RFID - Kleine Chips und große Hoffnungen!", 2006)
lhft_intern.bib::Vossiek2006c

Radiometer Design for Short Range Imaging at 2.5 THz - Huber, K.; Biber, Stephan; Rehm, Guenther; Schulz, R.; Brand, Hans; Schmidt, Lorenz-Peter (Proceedings of the Open Symposium on Propagation and Remote Sensing, 2002)
UnivIS-Import:2015-04-16:Pub.2002.tech.IE.LEH.radiom

Raman-Faserlaser: Gelbe Strahlquellen für die Medizin- und Messtechnik - Engelbrecht, Rainer; Hagen, Johannes; Siekiera, Alexander (Faser-Scheibe-Slab 3, Bayerische Laserseminare, 27. März 2007, 2007)
UnivIS-Import:2015-04-16:Pub.2007.tech.IE.LEH.ramanf

Raman-Faserlaser: Neue Wellenlängen aus dem Lichtwellenleiter - Engelbrecht, Rainer (Bayerische Laserseminare: Faser, Scheibe, Slab - Neue Laserkonzepte für neue Anwendungen, Erlangen, 29.04., 2003)
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.ramanf

Raman-Faserverstärker und Raman-Faserlaser: Grundlagen und Beispiele - Engelbrecht, Rainer (Workshop der VDE ITG-Fachgruppe 5.3.1 (Modellierung photonischer Komponenten und Systeme), 2015)
lhft_intern.bib::engelbrecht15a

Rauschunterdrückung und Pulsformung in faseroptischen Sagnac Interferometern (NOLM) - Wietfeld, André; Schmauß, Bernhard; Meißner, Markus; Leuchs, Gerd (ITG Workshop Modellierung photonischer Komponenten und Systeme, Stuttgart, November, 2001)
UnivIS-Import:2015-04-16:Pub.2001.tech.IE.LEH.rausch_7

Rauschunterdrückung und Pulsformung mit einem Faser Sagnac Interferometer - Wietfeld, André; Meißner, Markus; Schmauß, Bernhard (Workshop der ITG Fachgruppe 5.3.1., 2001)
UnivIS-Import:2015-04-16:Pub.2001.tech.IE.LEH.rausch

Rayleigh-Backscattering Impact on Performance of NOLM-Based Phase-Preserving Optical Limiters - Onishchukov, G.; Sponsel, K.; Stephan, C.; Roethlingshoefer, T.; Schmauß, Bernhard; Leuchs, Gerd (Photonics Society Summer Topical Meetings Series, IEEE, 2010)
lhft_intern.bib::Onishchukov10

Realtime 70 GHZ-Imaging System for Close Range Applications - Brand, Hans; Kreutzer, E; Vogel, M (IEEE, 2006)
The design principles for real time microwave imaging systems with multiple-target capability in close range applications are discussed. Target movements in usual traffic situations should be recognized even in severe weather conditions. An experimental approach to the problem leads to a quasi-optical mm-wave solution combined with a FM-radar- signal processing to obtain image data of azimuth and rang
lhft_intern.bib::thirty_years_LHFT_155

Realtime Laser Beam Steering and Calibration Method for Coherent Biomedical Distance and Motion Sensing - Schmidt, Marius; Sadeghi, Misha; Rahimi, Farnaz; Eskofier, Björn; Buglagil, Arda; Schmauß, Bernhard; Carlowitz, Christian (CLEO: Science and Innovations, CLEO: S and I 2024 in Proceedings CLEO 2024, Part of Conference on Lasers and Electro-Optics, 2024)
This paper presents a depth camera based 3D position tracking and calibration method for realtime millimeter-accuracy galvanometer laser beam steering that enables high sensitivity coherent optical distance and movement sensing for biomedical applications.
CRIS-Team Scopus Importer:2024-10-04

Recent advances in digital backward propagation algorithm for coherent transmission systems with higher order modulation formats - Schmauß, Bernhard; Asif, Rameez; Lin, Chien-Yu (SPIE 8284, 82840O, 2012)
Recent numerical and experimental studies have shown that coherent transmission with advanced modulation formats i.e. DP-QPSK and QAM are the promising candidates for next-generation systems with data rates of 100Gbit/s and above. Coherent detection is considered efficient along with digital signal processing (DSP) to compensate many linear effects in fiber propagation i.e. chromatic dispersion (CD) and polarization-mode dispersion (PMD). Despite of fiber non-linearities (NL), which are the major limiting factors, next-generation optical systems are employing higher order modulation formats in order to fulfil the ever increasing demand of capacity requirements. However, the channel capacity is limited at higher signal input powers because the system is operating in the non-linear regime. Due to this phenomenon the compensation of non-linearities is a topic of great interest and research these days, especially for long-haul fiber transmission. Digital backward propagation (DBP) algorithm has emerged as a promising and potentially capable candidate, which can jointly compensate fiber dispersion and non-linearities along with the coherent receiver. In this paper we give a detailed overview on the advancements in DBP algorithm based on different types of mathematical models i.e. Wiener (Asymmetric Method) and Wiener Hammerstein models (Symmetric Method). We also discuss the importance of optimized step-size selection, i.e. constant step-size and logarithmic step-size based split step Fourier methods, for simplified and computationally efficient implementation of DBP algorithm. Moreover, by means of numerical investigations we refer to recent system investigations to further improve the performance of DBP algorithm.
lhft_intern.bib::Schmauss2012

Recent developments and concepts leading to advanced microwave andmm-wave phased array antennas - Huder, B; Schmidt, Lorenz-Peter; Adelseck, B; Feldle, H; Dämpkes, H (International MMIC-Workshop ESA/ESTEC, 1991)
lhft_intern.bib::Schmidt22

Record 5.3 Gbit/s Transmission over 50m 1mm Core Diameter Graded-Index Plastic Optical Fiber - Visani, D.; Okonkwo, C.; Loquai, S.; Yang, H.; Shi, Y.; Van Den Boom, Henrie; Diteweig, A. M. H.; Tartarini, G.; Schmauß, Bernhard; Randel, S.; Koonen, A. M. J.; Tangdiongga, E. (OSA Optics and Photonics Congress, Advanced Photonics, BGPP Topical Meeting, Karlsruhe, 21.-24. Juni, 2010)
We report multi-Gbit/s capacity in 1-mm diameter graded index plastic optical fiber exploiting low-cost eye safe compliant transceivers. Transmission rates between 5.3 and 7.6 Gbit/s are achieved for lengths between 10 and 50 m using DM
lhft_intern.bib::Visani10

Recursive Phase Extraction for Holographic Localization of Incoherent FMCW Beacons - Lipka, Melanie; Sippel, Erik; Brückner, Stefan; Vossiek, Martin (ICMIM, Linz, 2020)
Radio-based localization systems are a vibrant field of scientific research with various use-cases in indoor environments. Particularly, the live tracking of freely moving objects offers significant value; however, such tracking requires high update rates and precise localization. An advanced approach with low computational effort is the holographic extended Kalman filter (HEKF), which has already achieved accuracy in the cm-range even with a moderate bandwidth. Hereby, the phase value is extracted from the peak of the spectrum requiring a maximum-search in the full spectrum. The computational effort in frequency-modulated-continuous-wave systems can be reduced by replacing the maximum search by calculating the evaluation bin. In this paper, a recursive method for the phase extraction for HEKFs in secondary radar systems with an incoherent beacon is presented and evaluated using a 24 GHz frequency-modulated-continuous-wave syste

Reduction of Nonlinear Phase Noise in DPSK Transmission Using a NALM - Stephan, Christian; Sponsel, Klaus; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE/LEOS Winter Topicals Meeting Series, 2009)
Performance of a NALM as phase-preserving amplitude 2R-regenerator in a DPSK transmission system has been investigated experimentally and numerically. A 3dB improvement of eye opening or alternatively a 3dB increase of fibre-launched power are demonstrated.
UnivIS-Import:2017-12-18:Pub.2009.tech.IE.LEH.reduct

Reduction of the Rayleigh-Backscattering Impact in Nonlinear Loop Mirrors by Dispersion Management - Röthlingshöfer, Tobias; Sponsel, Klaus; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (OSA Conference on Nonlinear Photonic, 2010)
UnivIS-Import:2016-06-01:Pub.2011.tech.IE.LEH.reduct

Reflection Ellipsometry with a Polarimetric Multistatic Array for Short Range Imaging Applications - Cenanovic, Amir; Gumbmann, Frank; Schmidt, Lorenz-Peter (Asia-Pacific Microwave Conference, 2011)
This paper presents an approach for the detection of dielectric layers on human bodies and the determination of their dielectric constant with single frequency measurement data in the W-band (75-110 GHz). The measurements were performed with a polarimetric multistatic array, which was optimized for short range applications. The scattering matrix of each resolution element was analyzed via the reflection ellipsometry method, adopted from optics. For millimeter wave imaging techniques, used in the field of nondestructive testing (NDT) and for security applications, this measurement approach offers an promising alternative to the time domain analysis, which requires broadband data.
lhft_intern.bib::Cenanovic2011b

Reflektivität und Abbildung von natuerlichen und technischen Objekten bei Submillimeterwellen - Brand, Hans; Brune, J (1993)
lhft_intern.bib::thirty_years_LHFT_311

Regenerative Backscatter Transponder Using the Switched Injection-Locked Oscillator Concept - Vossiek, Martin; Schäfer, Tobias; Becker, Dirk (IEEE MTT-S International Microwave Symposium 2008 (IMS 2008), 2008)
In this paper, a new backscatter transponder type is introduced. The developed transponder regenerates a modulated, phase-coherent high-power response/ replica to an interrogating CW radar signal. To create the amplified phasecoherent transponder response, the switched injection locked oscillator (SILO) concept is applied. Compared with a usual passive backscatter transponder - known e.g. from UHF RFID systems - the reading range of a SILO transponder is substantially increased. It is demonstrated that a reading range above 20 m is easily obtained even with a 5.8 GHz, 15 MBit/s system. © 2008 IEEE.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.regene
Keywords: Identification; Oscillators; Phase synchronization; Radar; Radio communication; Transponders

Regenerative Sampling Self-Mixing Receiver: A Novel Concept for Low Complexity Phase Demodulation - Carlowitz, Christian; Eßwein, Alexander; Weigel, Robert; Vossiek, Martin (IEEE International Microwave Symposium 2013, 2013)
In this paper, a novel low complexity receiver concept for high-order differential phase demodulation is introduced for the first time. With a first hardware demonstrator, a high data rate of 300 Mbit/s is achieved without requiring a synthesizer for downconversion. A phase sensitive regenerative sampling approach is employed that integrates both low noise amplifier and automatic gain control using a free running switched injection-locked oscillator with no need for stabilization by a phase locked loop. Differential phase detection is achieved by quadrature self-mixing the regenerated signal with one path delayed by the symbol period. This approach is particularly attractive in combination with the switched injection-locked oscillator due to its constant high output power that allows for matching the mixer's best operating point. The proposed concept is demonstrated at 5.5 GHz with 8th order differential phase shift keying and a symbol rate of 100 MBaud/s. A short range data rate of 300 Mbit/s is achieved at a bit error rate below 1e-3. © 2013 IEEE.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.regene
Keywords: Injection-locked oscillators; Receiver architectures; Signal sampling; Wideband communication

Registration of Image Sequences from Experimental Low-Cost Fundus Camera - Kolar, Radim; Höher, Bernhard; Odstrcilik, Jan; Schmauß, Bernhard; Jan, Jiri (6th International Workshop in Biomedical Image Registration, 2014)
This paper describes new registration approach for registration of low SNR retinal image sequences. We combine two approaches - Fourier-based method for large shift correction and Lucas-Kanade tracking for small shift and rotation correction. We also propose method for evaluation of registration results, which uses spatial variation of minimum value in intensity profiles through blood-vessels. We achieved precision of registration below 2.1 pixels, which is acceptable with regards to image SNR (around 10dB). The final averaging of registered sequence leads to improvement of image quality and improvement in SNR over 10 d
lhft_intern.bib::Radim2014

Rein optische 2R-Regeneration unter Ausnutzung der Selbstphasenmodulation - Striegler, Arne; Wietfeld, André; Schmauß, Bernhard (Conf. Proc., 4. ITG Fachtatung Photonische Netze, ITG Fachbericht 175, 2003)
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.reinop

Relative intensity noise (RIN) of near infrared DFB and VCSEL diode lasers under the influence of back reflections - Lins, B.; Engelbrecht, Rainer; Zinn, P.; Buchtal, R.; Schmauß, Bernhard (8th International Conference on Tunable Diode Laser Spectroscopy, TDLS 2011, 2011)
lhft_intern.bib::B.Lins2011

Reliability of Printed Microwave Electronics - Neermann, Simone; Franke, Jörg; Sippel, Mark; Lomakin, Konstantin; Gold, Gerald (IEEE 71ST ELECTRONIC COMPONENTS AND TECHNOLOGY CONFERENCE (ECTC 2021), 2021)
CRIS-Team WoS Importer:2021-10-29

Remote local positioning radar - Wiebking, Leif; Glanzer, M.; Mastela, Dariusz; Christmann, Mark; Vossiek, Martin (IEEE Radio and Wireless Conference, 2004)
A remote local positioning radar (LPR) systems was developed for logistics application. In the system, the round-trip time-of-flight between a transponder unit and the base stations was measured. The main advantage of such system are low costs of the mobile units, the high update rate, and low power consumption. The system configuration with a mobile base station is similar to global positioning system (GPS) with a mobile receiver unit and satellites at known positions. The system is costly and easily implementable for tracking different objects at the same time in an indoor or outdoor environment with a precision of less than 20 cm by using a time-of-arrival based measurement principle.
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.remote

Resource Allocation for a Distributed Antenna System - Goodarzi, Meysam (Friedrich-Alexander-Universität Erlangen-Nürnberg, 2017)

Review of Optical Frequency Domain Reflectometry Methods for Optical Fiber Sensors - Engelbrecht, Rainer; Werzinger, Stefan; Köppel, Max; Saur, G; Schmauß, Bernhard (26th International Conference on Plastic Optical Fibres (POF2017), 2017)
lhft_intern.bib::Engelbrecht2017

RF Characterization of the Homogeneity of Sintered Micro- And Nanoparticle Silver Inks for Printed Electronics - Neermann, Simone; Franke, Jörg; Sippel, Mark; Lomakin, Konstantin; Gold, Gerald (2021 14th International Congress: Molded Interconnect Devices, MID 2021 - Proceedings, 2021)
A significant problem of printed electronics which is hardly considered in science is the inhomogeneous sintering of printed conductive silver micro- and nanoparticle inks. This so called skinning effect as well as its consequences such as accompanying economically suboptimal processes, reduced conductivity, poor surface quality and possible mechanical reliability problems have not yet been investigated. On the other hand, there is a lack of characterization methods to analyze this effect with sufficient accuracy so that it can be observed at all in order to optimize existing processes, materials and thus end products. In this paper the concept of a novel electrical characterization method is presented. The basis of the method is the skin effect, not to be confuse with the skinning of the ink, which describes the penetration of electromagnetic fields in metals that decreases with frequency, thus enabling a correlation between electrical transmission properties and the conductivity profile of printed and sintered lines. This allows for characterization of the effects from various sintering parameters on printed structures by means of appropriate measurement technology. The expected measurement frequencies are in the three-digit MHz range, depending on the DC conductivity. If additional measurements at higher frequencies are available, the penetration depth is so small that conclusions about surface roughness of the sintered structure can be drawn.
CRIS-Team Scopus Importer:2021-04-02
Keywords: characterization; homogeneity; Printed Electronics; RF; sintering

RFID - Einbindung der radiofrequenten Identifikation in bestehende Geschäftsprozesse - Was ist technisch machbar und betriebswirtschaftlich sinnvoll? - Vossiek, Martin (IHK-Seminar - Die Brücke zwischen Informationsfluss und Warenfluss, Seminar der IHK Braunschweig, 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.rfidei

RF Identification and Localization - Recent Steps towards the Internet of Things in Metal Production and Processing - Vossiek, Martin; Miesen, Robert; Wittwer, Joachim (18th International Conference on Microwaves, Radar, and Wireless Communications MIKON-2010, 2010)
This paper gives an overview on recent radio frequency local positioning and identification techniques applied in steel production and processing. It is shown that it is required to combine different radio technologies in order to track and trace the goods involved in the manufacturing processes reliably and continuously. In addition the applied components must be carefully adapted to the given application area. The presented RF technologies are key components for the future internet of things and the presented applications illustrate both, the huge potential as well as the challenges involved with applying modern radio systems in harsh manufacturing processes.
lhft_intern.bib::Vossiek2010

RFID ? Grundlagen der Radiofrequenten Identifikation - Vossiek, Martin (Radio Techniques and Technologies for Commercial Communication and Sensing Applications, RadioTecC 2006, 2006)
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.rfidgr

RFID Hardware and Physical Layer: Status and Development Directions (W13) - State of the Art and Recent Developments in RFID Localization Technology - Miesen, Robert; Parr, Andreas; Vossiek, Martin (43th European Microwave Week, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.rfidha

RF-sensor for a local position measurement system - Stelzer, Andreas; Fischer, Alexander; Weinberger, F.; Vossiek, Martin (8th NDE Symposium: Nondestructive Detection and Measurement for Homeland Security Conference, 2003)
In this paper a novel local position measurement (LPM) technology is presented. The LPM system operates in the 5GHz ISM band and consists of lightweight transponders of which the 3-D position is measured, and base stations located around the measurement field. Transponder and base stations operate similar to conventional radar systems and consist of RF electronics as well as signal processing elements. The RF-part in the transponders is the key element for the position measurement system. The measurement accuracy of the LPM system is in the range of some centimeters despite a high measurement rate of 1000 measurements per second.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.rfsens
Keywords: 3-D positioning; Distance measurement; Local position measurement; RF-front-end

Rigorous Computation of the Frequency Dependant Properties of Filters and Coupled Resonators Composed from Transverse Microstrip Discontinuities - Schmidt, Lorenz-Peter (European Microwave Conference, 1980)
A numerically efficient method is presented, which yields the propagation constants and the field distributions of basic and higher order modes of shielded microstrip lines. Upon this basic a mode matching technique is applied in order to calculate the frequency dependant generalized scattering matrices of transverse microstrip discontinuities like impedance steps and open ends. From these discontinuities several microstrip components like filters, transverse gaps, and coupled resonators can be composed. Important effects like convergence behaviour, numerical stability, and the influence of higher order propagating and not propagating modes have been studied, and some interesting numerical and experimental results are presente
lhft_intern.bib::Schmidt80c

Robust DOA Estimation of SSR Signals for Aircraft Positioning - Reck, Christoph; Berold, U.; Schmidt, Lorenz-Peter (RWW, 2011)
lhft_intern.bib::Reck2011

Robust Light Spot Hydrophone with Calibration Control for the Measurement of Medical Ultrasound Shock Waves - Engelbrecht, Rainer; Schulz, R.; Hagen, J.; Pfister, T.; Granz, B.; Nanke, R.; Fehre, J. (Proceedings, Sensor 2005 (12th Int. Conf. Sensor 2005, Nürnberg 2005)May, 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.robust

Robust MSE-Balancing Hierarchical Linear/Tomlinson-Harashima Precoding for Downlink Massive MU-MIMO Systems - Zarei, Shahram; Gerstacker, Wolfgang; Weigel, Robert; Vossiek, Martin; Schober, Robert (IEEE Transactions on Wireless Communications, 2018)
In this paper, we propose a robust minimum maximum mean square error Tomlinson-Harashima precoding (Min-Max-MSE THP) scheme and a low-complexity robust Min-Max-MSE hierarchical linear/THP (HL-THP) scheme for downlink massive multiuser multiple-input-multiple-output (MU-MIMO) systems with imperfect channel state information (CSI) at the transmitter. The proposed robust Min-Max-MSE HL-THP scheme comprises an inner linear beamformer (BF), which is designed based on second-order CSI statistics, and outer THP modules, which exploit the instantaneous overall CSI of the cascade of the actual channel and the inner BF. Thereby, the user terminals are divided into groups, where for each group a THP module successively mitigates the intra-group interference, whereas the inter-group interference is canceled by the inner BF. To ensure fairness, we adopt the maximization of the asymptotic signal-to-leakage-plus-noise ratio in the large system limit and the Min-Max-MSE as an optimization criterion for designing the inner BF and the per-group THP modules, respectively. Our analytical and simulation results show that the proposed robust Min-Max-MSE HL-THP scheme achieves a substantially improved performance in terms of the Max-MSE, maximum bit error rate, and minimum rate compared to linear regularized zero-forcing precoding. Moreover, the performance loss of the proposed robust Min-Max-MSE HL-THP scheme compared to the robust Min-Max-MSE THP scheme is small. In addition, our complexity analysis reveals that the proposed robust Min-Max-MSE HL-THP scheme has a much lower computational complexity than the Min-Max-MSE THP scheme. Hence, the robust Min-Max-MSE HL-THP scheme provides a favorable tradeoff between complexity and performanc
lhft_intern.bib::Zarei2018a
Keywords: Precoding; Robustness; Interference; Computational complexity; Optimization; Wireless communication

Robust polymer planar bragg grating sensors embedded in commercial-grade composites - Kefer, Stefan; Sauer, Theresia; Hessler, Steffen; Kaloudis, Michael; Schmauß, Bernhard; Hellmann, Ralf (Polymers, 2020)
This contribution demonstrates the functionality of polymer planar Bragg grating (PPBG) sensors integrated into commercial-grade carbon fiber reinforced polymer (CFRP) components. Multiple CFRP specimens are generated by curing a stack of pre-impregnated fibers inside of a heated mechanical press, exposing the polymer sensor to a pressure of 7 bar and a temperature of 120 °C for 2 h. After integration, the sensor still exhibits a strong and evaluable signal. Subsequent flexural experiments reveal a linear response of the integrated sensor's Bragg wavelength to the CFRP specimen's maximum deflection. Additional findings demonstrate that the embedded PPBG can be used to detect plastic deformations of a CFRP workpiece, whereas a linear correlation of plastic deformation to the resulting Bragg signal offset is determined. A plausibility check of the obtained results is delivered by a comparison of three-point flexural experiments on bulk CFRP workpieces, without integrated sensors and additional specimens featuring external optical sensors affixed to their surface. It is found that PPBGs based on cyclic olefin copolymers are able to overcome the temperature-related limitations of traditional polymer-based optical sensors and can thus be directly integrated into commercial-grade composites during production.
CRIS-Team Scopus Importer:2020-04-14
Keywords: Bragg grating sensors; Carbon fiber reinforced polymers; Cyclic olefin copolymers

Rx-Tx Analog Front-End Module with 2 x 96 Channels for mm-Wave ImagingSystems - Schiessl, A.; Juenemann, R.; Schmidt, Lorenz-Peter (42nd European Microwave Week, 2012)
Active millimeter-wave imaging systems are increasingly utilized in security, medical and industrial applications. At E-Band frequencies, such systems integrate more than three thousand antennas on 2 m × 1 m aperture. Commercial success of those systems requires cost efficient but precise manufacturing technologies to build highly integrated modular mm-wave front ends. Here, a module for a new sparse imaging array architecture is presented. The module is manufactured using a unique mm-wave chip-on-board technology. It operates from 70 GHz to 80 GHz, and integrates 48 MMICs and several thin film ceramic components.
lhft_intern.bib::Schiessl2012euwm

Sapphire-Based Planar Bragg Grating Devices - Kefer, Stefan; Schmauß, Bernhard; Hellmann, Ralf (Proceedings - 28th International Conference on Optical Fiber Sensors, OFS 2023, 2023)
This study reports on the long-term stability and the high-temperature capability of sapphire-based photonic crystal waveguides with integrated Bragg gratings. Furthermore, their Bragg grating reflectivity as well as their temperature sensitivity is quantified.
CRIS-Team Scopus Importer:2024-12-16

Sapphire Photonic Crystal Waveguides with Integrated Bragg Grating Structure - Kefer, Stefan; Roth, Gian Luca; Zettl, Julian; Schmauß, Bernhard; Hellmann, Ralf (Photonics, 2022)
This contribution demonstrates photonic crystal waveguides generated within bulk planar sapphire substrates. A femtosecond laser is used to modify the refractive index in a hexagonal pattern around the pristine waveguide core. Near-field measurements reveal single-mode behavior at a wavelength of 1550 nm and the possibility to adapt the mode-field diameter. Based on far-field examinations, the effective refractive index contrast between the pristine waveguide core and depressed cladding is estimated to 3·10−4. Additionally, Bragg gratings are generated within the waveguide core. Due to the inherent birefringence of Al2O3, the gratings exhibit two distinct wavelengths of main reflection. Each reflection peak exhibits a narrow spectral full width at a half maximum of 130 pm and can be selectively addressed by exciting the birefringent waveguide with appropriately polarized light. Furthermore, a waveguide attenuation of 1 dB cm−1 is determined.
CRIS-Team Scopus Importer:2022-04-29
Keywords: Bragg grating; depressed cladding; femtosecond laser; integrated photonics; photonic crystal waveguide; sapphire

SAR Acquistion for Hyerthermia Applictors Using a Muscle Equivalent Phantom Fluid - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard; Seegenschmiedt, Heinrich; Sauer, R. (Proc. of 2. Workshop of COST 244 Project, Instrumentation and Measurements in Bioelectromagnetism, 1994)
UnivIS-Import:2015-04-16:Pub.1994.tech.IE.LEH.saracq

SAR Acquistion for Hyerthermia Applictors Using a Muscle Equivalent Phantom Fluid - Erb, J; Engelbrecht, Rainer; Schaller, G; Seegenschmiedt, H; Sauer, R (1994)
lhft_intern.bib::thirty_years_LHFT_371

SAR Based Non-Destructive Evaluation of Irregularly Shaped Objects with Simultaneous Estimation of Geometry and Permittivity - Ullmann, Ingrid; Adametz, Julian; Vossiek, Martin (16th European Radar Conference (EuRAD 2019), 2019)
The geometrically correct registration of subsurface structures that are embedded in a medium with unknown shape and permittivity - e.g. a small defect in fiber or ceramic components - is one of the most challenging tasks in radar imaging. This paper presents a new methodology for subsurface synthetic aperture radar (SAR) imaging with integrated estimation of geometry and permittivity applicable for non-destructive evaluation (NDE). Two SAR measurements are performed, one scanning the device under test (DUT) from the front side, the second scanning the DUT from the backside. By comparing the contour profile derived from the front side/ backside measurement with an SAR image of the complete DUT reconstructed under the assumption of free-space propagation, the permittivity and complete contour of the DUT are estimated. A high-resolution image is then reconstructed with an adapted subsurface backprojection algorithm that considers the contour and permittivity estimates correctly. Experimental results with a polyethylene DUT with two small embedded defects are presented that validate the proposed technique. It is shown that with the novel approach good estimations of shape and permittivity as well as geometrically correct high resolution images can be achieved

SAR-Distribution in a Medical Attendant near the BDS-2000 Deep Hyperthermia System - Schaller, Gerhard; Engelbrecht, Rainer; Erb, J. (Meeting of the Europ. Soc. Hyperthermia Oncology ESHO, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.sardis

SAR-Distribution in a Medical Attendant near the BDS-2000 Deep Hyperthermia System - Schaller, G; Engelbrecht, Rainer; Erb, J (1995)
lhft_intern.bib::thirty_years_LHFT_377

SAR Interferometric and Tomographic Imaging of Saturn’s Moon Enceladus Using Strongly Perturbed Orbits - Benedikter, Andreas; Krieger, Gerhard; Rodríguez-Cassolà, Marc; Hussmann, Hauke; Wickhusen, Kai; Stark, Alexander; Stelzig, Michael; Vossiek, Martin (EUSAR 2022; 14th European Conference on Synthetic Aperture Radar, 2022)
In the frame of DLR’s Enceladus Explorer Initiative, we explore the potential of a SAR interferometric and tomographic orbiter for topography and deformation measurements, as well as 3-D imaging of the Enceladus ice crust. The stringent repeating ground track requirement for forming interferometric repeat-pass baselines paired with the strong gravitational perturbation by Saturn largely constrains the solutions for candidate orbits. Potential orbits have varying repeat-pass baselines between tens of meters and few kilometers. We assess the potential of a dual-frequency SAR instrument (Ka- and P-band) based on such orbits for repeat-pass SAR interferometry and tomography and provide first performance estimate

SAR-like Localization of RFID Tags for Non-uniform Trajectory - Kunkel, Sebastian; Huang, Ming-Shih; Bieber, Robert; Vossiek, Martin (40th European Microwave Conference, 2010)
In this paper we present a new principle for localization of backscatter RFID tags. A new algorithm comparable to synthetic aperture radar on a non-uniform trajectory is proposed. The performance is verified with measurement data acquired by a multi sensor platform which comprises radar, imaging and RFID. The identified RFID transponder positions are presented with augmented-reality visualization. The new radar approach called SAR-like is shown to have similar performance as SAR at an apparently lower computational cost.
lhft_intern.bib::Kunkel2010

SAR Measurements of Coaxial Antennas in a Muscle Equivalent Water Phantom - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard; Seegenschmiedt, Heinrich; Fietkau, Rainer; Sauer, R.; Ross, D. (Hyperthermia in Clinical Oncology - In Memory of Dr. Mildred Scheel, 1993)
UnivIS-Import:2015-04-16:Pub.1993.tech.IE.LEH.sarmea_0

SAR Measurements of Coaxial Antennas Used for Interstitial/Endocavitary HT - Erb, J; Engelbrecht, Rainer; Schaller, G; Roos, D; Seegenschmiedt, H; Fietkau, R; Sauer, R (1993)
lhft_intern.bib::thirty_years_LHFT_306

SAR Measurements of Coaxial Antennas Used for Interstitial/Endocavitary HT. - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard; Ross, D.; Seegenschmiedt, Heinrich; Fietkau, Rainer; Sauer, R. (13^th Meeting of the Europ. Soc. Hyperthermia Oncology ESHO, 1993)
UnivIS-Import:2015-04-16:Pub.1993.tech.IE.LEH.sarmea

SAW based delay locked loop concept for VCO linearization in FMCW radar sensors - Christmann, Mark; Vossiek, Martin; Smith, R.; Rodet, G. (33rd European Microwave Conference, EuMC, 2003)
A novel linearization approach for VCOs in FMCW radar sensors is proposed. The principle relies on a SAW delay line that is applied to generate a reference beat signal. With the proposed concept it is possible to realize a Delay Locked Loop that generates a pre-distorted VCO tuning voltage. The system can be realized in CMOS technology. For the verification of the concept a test system was set up where the logic is implemented in a FPGA. In this paper the linearization principle and the test results of the demonstrator are presented. © 2003 EUMA.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.sawbas

SAW RFID Tag Spatial Division Multiple Access Based on 3D Reflector Response Localization Using a Wideband Holographic Approach - Caldero Bardaji, Pau; Gareis, Matthias; Vossiek, Martin (IEEE Journal of Microwaves, 2022)
Surface acoustic wave (SAW) radio-frequency identification (RFID) has high potential for industrial applications, where automated identification and localization of assets represent the backbone of process controlling and logistics. However, in situations where multiple tags are simultaneously interrogated, the response patterns corresponding to the hard-coded reflectors are prone to overlap, preventing their association with the corresponding tags and, hence, the correct tag decoding. Identification and localization of multiple SAW RFID tags are addressed in this work under this challenging effect, known as collision, with a multi-antenna mobile robot-based synthetic aperture approach. Using the estimation of the spatial probability density functions of the SAW tag reflectors over a given interrogation aperture, the received impulse responses can be resolved in three dimensions and clustered with respect to their estimated locations. The performance of the proposed approach to associate and localize the signals from multiple tags was evaluated theoretically and experimentally.<br
Keywords: 3D localization; anti-collision; RFID; SAW; SDMA

SBS shaping and suppression by arbitrary strain distributions realized by a fiber cioling machine - Engelbrecht, Rainer; Mueller, M.; Schmauß, Bernhard (2009 IEEE / LEOS Winter Topical Meeting, Innsbruck, Austria, 12.-14. Jan., 2009)
Experimental results of coiled fibers with a permanent arbitrary distribution of longitudinal strain along the fiber in order to shape or to suppress significantly the gain spectrum of Stimulated Brillouin Scattering (SBS) are presented.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.sbssha

SBS-Suppression in Variably Strained Fibers for Fiber-Amplifiers and Fiber-Lasers with a High Spectral Power Density - Engelbrecht, Rainer; Hagen, J.; Schmidt, M. (XV Int. Symp. on Gas Flow, Chemical Lasers and High-power Lasers, GCL/HPL 2004, Prague. Proceedings of SPIE, 2004)
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.sbssup