Fasergekoppelte NIR-Diodenlaser-Spektrometer zur simultanen und isotopen-aufgelösten Messung von CO und CO_2: Anwendungen in Plasma-Diagnostik und Bodengasanalyse - Engelbrecht, Rainer; Lau, S.; Salffner, K.; Löhmannsröben, Hans-Gerd (VDI Fortschrittsberichte 1959, Tagung OPTAM 2006, Mannheim, 2006)
UnivIS-Import:2015-04-16:Pub.2006.tech.IE.LEH.faserg

Faseroptische Sensorik - Grundlagen und aktuelle Forschungsthemen - Werzinger, Stefan; Engelbrecht, Rainer (Workshop Fasersensorik - Märkte, Konzepte, Anwendungen., 2015)
lhft_intern.bib::werzinger15

Fastest thickness measurements with a Terahertz time-domain system based on electronically controlled optical sampling - Yahyapour, Milad; Jahn, Angelika; Dutzi, Katja; Puppe, Thomas; Leisching, Patrick; Schmauß, Bernhard; Vieweg, Nico; Deninger, Anselm (Applied Sciences, 2019)
We apply a fast terahertz time-domain spectroscopy (TDS) system based on electronically controlled optical sampling (ECOPS) to contact-free thickness gauging. Our setup achieves a measurement speed of 1600 terahertz pulse traces per second, which-to our knowledge-represents the fastest thickness measurement performed with any terahertz system to-date. Using a silicon wafer as a test sample, we compare data of the ECOPS experiment to results obtained with a conventional terahertz TDS system and a mechanical micrometer gauge. We show that all systems provide consistent results within the measurement accuracy. Moreover, we perform thickness measurements of a rapidly moving sample and characterize the ECOPS setup with respect to time-domain dynamic range, signal-to-noise ratio, and spectral properties.
CRIS-Team Scopus Importer:2019-06-18
Keywords: ECOPS; Non-destructive testing; Real-time inspection; Terahertz time-domain instrumentation; Thickness gauging

Fast Millimeter Wave Imaging - Brand, Hans (Springer Netherlands, 1985)
lhft_intern.bib::thirty_years_LHFT_159

Fast Multistatic Measurement System for Short Range Imaging Radar Development - Schießl, Andreas; Ahmed, S. S.; Genghammer, A.; Schmidt, Lorenz-Peter (12th URSI Commission-F Triennial Open Symposium on Radio Wave Propagation and Remote Sensing, 2011)
lhft_intern.bib::Schiessl11

Fast SAR-Scans of Interstitial Microwave Dipole Antennas in a Muscle Equivalent Water Phantom - Erb, J; Engelbrecht, Rainer; Schaller, G; Roos, H; Seegenschmiedt, R; Fietkau, R; Sauer, R (1993)
lhft_intern.bib::thirty_years_LHFT_305

Fast SAR-Scans of Interstitial Microwave Dipole Antennas in a Muscle Equivalent Water Phantom - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard; Roos, D.; Seegenschmiedt, Heinrich; Fietkau, Rainer; Sauer, R. (41st Ann. Meeting of the Radiation Research Society and the 13th Annual Meeting of the North American Hyperthermia Society, 1993)
UnivIS-Import:2015-04-16:Pub.1993.tech.IE.LEH.fastsa

Fast switching between direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS) for the investigation of resolution requirements - Lins, Bastian; Engelbrecht, Rainer; Schmauß, Bernhard (International Conference on Field Laser Applications in Industry and Research, FLAIR 2011, 2011)
UnivIS-Import:2015-04-16:Pub.2011.tech.IE.LEH.fastsw

Fast thickness gauging with an ECOPS-based terahertz time-domain system - Yahyapour, M.; Jahn, A.; Dutzi, K.; Puppe, T.; Leisching, P.; Schmauß, Bernhard; Vieweg, N.; Deninger, A. (Proceedings of SPIE - The International Society for Optical Engineering, 2020)
We employ thickness gauging with a fast terahertz time-domain spectroscopy (TDS) system based on electronically controlled optical sampling (ECOPS) and compare the results with those of a benchmark conventional terahertz TDS system and a mechanical micrometer gauge. The results of all technologies are in good agreement. We show that the ECOPS system is suitable for fast inline thickness measurements, owing to high measurement rate of 1600 traces per second. Moreover, we characterize the system with respect to signal quality. The time-domain dynamic range is ∼60 dB for a single-shot measurement, and ∼90 dB with 1000 trace averages, which are completed within less than a second (i.e., 0.625 seconds). The time-domain signal-to-noise ratio amounts to ∼50 dB and ∼80 dB for 1 and 1000 averages, respectively.
CRIS-Team Scopus Importer:2020-05-02
Keywords: ECOPS; Non-destructive testing; Real-Time inspection; Terahertz time-Domain instrumentation; Thickness gauging

FAU-Lehrstuehle Kooperieren in der Forschung von Schluesseltechnologie - Brand, Hans (Opto-Elektronik-Magazin, 1989)
lhft_intern.bib::thirty_years_LHFT_267

Feasibility of Additively Manufactured Tunable Liquid Crystal Loaded Dielectric Waveguides - Tesmer, Henning; Gold, Gerald; Bachbauer, Felix; Polat, Ersin; Sippel, Mark; Jakoby, Rolf; Vossiek, Martin; Maune, Holger (IEEE Microwave and Wireless Components Letters, 2021)
This paper investigates the feasibility of the combination of additive manufacturing and liquid crystal (LC) loaded dielectric waveguides (DWGs) at W-band (75 to 110 GHz). The waveguide is extruded such that it has a cavity in its center, used for LC hosting. Reproducible cross sections are achieved along the DWG and high agreement in differential phase shift and figure-of-merit (FoM) are obtained when the DWG is biased electrically or magnetically. De-embedding the structure shows attenuation constants between 0.12 dB/cm to 0.33 dB/cm which lead to a high FoM in the range of 100 °/dB to 160 °/dB. According to simulations higher values are obtainable if larger LC cavities are realized.<br
Keywords: Liquid Crystal; Additive Manufacturing; Phase Shifter; Dielectric Waveguide; mm-Wave Components; Reconfigurable Devices

Feasibility of Automotive Radar at Frequencies beyond 100 GHz - Köhler, Mike; Hasch, Juergen; Bloecher, Hans Ludwig; Schmidt, Lorenz-Peter (International Journal of Microwave and Wireless Technologies, 2012)
Radar sensors are used widely in modern driver assistance systems. Available sensors nowadays often operate in the 77 GHz band and can accurately provide distance, velocity, and angle information about remote objects. Increasing the operation frequency allows improving the angular resolution and accuracy. In this paper, the technical feasibility to move the operation frequency beyond 100 GHz is discussed, by investigating dielectric properties of radome materials, the attenuation of rain and atmosphere, radar cross-section behavior, active circuits technology, and frequency regulation issues. Moreover, a miniaturized antenna at 150 GHz is presented to demonstrate the possibilities of high-resolution radar for car
UnivIS-Import:2015-03-09:Pub.2012.tech.IE.LEH.feasib

Feasibility of automotive radar at frequencies beyond 100 GHz - Köhler, Mike; Hasch, Juergen; Bloecher, Hans Ludwig; Schmidt, Lorenz-Peter (International Journal of Microwave and Wireless Technologies, 2013)
Radar sensors are used widely in modern driver assistance systems. Available sensors nowadays often operate in the 77 GHz band and can accurately provide distance, velocity, and angle information about remote objects. Increasing the operation frequency allows improving the angular resolution and accuracy. In this paper, the technical feasibility to move the operation frequency beyond 100 GHz is discussed, by investigating dielectric properties of radome materials, the attenuation of rain and atmosphere, radar cross-section behavior, active circuits technology, and frequency regulation issues. Moreover, a miniaturized antenna at 150 GHz is presented to demonstrate the possibilities of high-resolution radar for car
lhft_intern.bib::Koehler2012

Feasibility of Manufacturing Dielectric Image Lines by Using Laser-Based Directed Energy Deposition of Polymers - Wittmann, Alexander; Bader, Tobias; Alidoust Chamandani, Saeed; Hentschel, Oliver; Schmidt, Michael; Gold, Gerald (IEEE Access, 2023)
The laser-based directed energy deposition of polymers (DED-LB/P) is an additive manufacturing process which offers the possibility to build up 3D structures with a high level of individualization on free-form surfaces. In this article, an absorber free DED-LB/P process with a thulium-doped fiber laser is presented for the first time to produce dielectric image lines (DIL) consisting of polypropylene (PP) for high frequency applications. This type of transmission line has advantages over the commonly used stripline technology due to its low signal attenuation, especially at high frequencies, but is currently hardly found in mass-market applications because no suitable manufacturing technology has been established for it yet. The steadily increasing demand of higher bandwidth in telecommunication or increased resolution of radar sensors leads to higher application frequencies and alternative interconnect technologies will become more important as they significantly define the achievable overall system performance. Based on the fabricated low-loss DILs in this study, DED-LB/P could represent such an alternative manufacturing process for future RF-applications.<br
Keywords: additive manufacturing; dielectric image lines; directed energy deposition; laser polymer deposition

Feasibility of using optoelectronic measurement of hand movement for characterizing hand function in rheumatoid arthritis - Coppers, Birte; Heinrich, Simon; Phutane, Uday; Berisha, Dardan; Tascilar, Koray; Kleyer, Arnd; Simon, David; Bräunig, Johanna; Penner, Johann; Vossiek, Martin; Schönau, Johanna; Bayat, Sara; et al. (75th EULAR (European Alliance of Associations for Rheumatology), European Congress of Rheumatology 2022, 2022)

Feldsimulation interstitieller Mikrowellenapplikatoren - Erb, J.; Schaller, Gerhard; Engelbrecht, Rainer; Seegenschmiedt, Heinrich (59. Physikertagung Berlin, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.feldsi

Feldsimulation interstitieller Mikrowellenapplikatoren - Erb, J; Schaller, G; Engelbrecht, Rainer; Seegenschmiedt, H (1995)
lhft_intern.bib::thirty_years_LHFT_373

Festschrift ueber den Tag der Erd-Fernerkundung - Brand, Hans (2004)
lhft_intern.bib::br04

Fiber as a temperature sensor with portable Correlation-OTDR as interrogator - Azendorf, Florian; Lawin, Mirko; Dochhan, Annika; Schmauß, Bernhard; Spinty, Florian; Eiselt, Michael (Photonische Netze - 21. ITG-Fachtagung, 2020)
In this paper, we report on the integration of a Correlation-OTDR into a portable unit (30 cm x 30 cm), based on a multi-processor system on chip (MPSoC) and a small formfactor pluggable (SFP) 2.5G transceiver. Going beyond telecommunication applications, this system is demonstrated for temperature measurements, based on the change of propagation delay with temperature in a short section of optical fiber. The temperature measurement accuracy is investigated as a function of the fiber length from 4 to 25 meters.
CRIS-Team Scopus Importer:2021-04-19
Keywords: Fiber as a sensor; Latency; Optical time domain reflectometry; Propagation delay; Sensing

Fiber-Based Compensation of IXPM-Induced Timing Jitter - Striegler, Arne; Schmauß, Bernhard (IEEE Photonics Technology Letters, 2004)
We derive from an analytical approach conditions to cancel out timing jitter by balancing intra channel effects in subsequent link sections. In numerical simulations we proof the applicability of a fiber based compensating structure at 40Gbit/s. © 2003 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2004.tech.IE.LEH.fiberb

Fiber Based Compensation of IXPM Induced Timing Jitter - Striegler, Arne; Wietfeld, André; Schmauß, Bernhard (MF72, OFC 2004, Los Angeles, USA, Februar, 2004)
We derive from an analytical approach conditions to cancel out timing jitter by balancing intra channel effects in subsequent link sections. In numerical simulations we proof the applicability of a fiber based compensating structure at 40Gbit/s. © 2003 Optical Society of America.
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.fiberb_2

Fiber Bragg Grating Filter for Spectral Reshaping of Directly Modulated Laser Diode with 10 Gbit/s NRZ-OOK Modulation Format - Siekiera, A.; Engelbrecht, Rainer; Schmauß, Bernhard (OSA Optics and Photonics Congress, Advanced Photonics, BGPP Topical Meeting, Karlsruhe, 21.-24. Juni, 2010)
lhft_intern.bib::Siekiera10b

Fiber Bragg Gratings in Polarization Maintaining Specialty Fiber for Raman Fiber Lasers - Siekiera, Alexander; Engelbrecht, Rainer; Neumann, R.; Schmauß, Bernhard (Physics Procedia, 2010)
The fabrication of fiber Bragg gratings (FBG) in highly nonlinear specialty fibers for Raman fiber lasers (RFL) is described. Besides the special properties of FBGs in polarization maintaining (PM) fibers that have to be considered with regard to an optimized laser performance, a method for the post-fabrication tuning of the grating reflectivity by exploiting the nonlinear photosensitivity characteristic of the fiber is presented. Experimental results for a RFL setup with a cavity length of 3 m and FBGs directly inscribed into the active Raman fiber are discussed.
lhft_intern.bib::Siekiera10
Keywords: Fiber Bragg grating; Raman fiber laser; Fiber photosensitivity

Fiber Bragg Grating Temperature Sensing in Fuel Cells - Renner, Esther; Römpke, Sonja-Maria; Mull, Sophie; Braun, Katharina; Weiß, Lukas; Wensing, Michael; Schmauß, Bernhard (2024 IEEE Photonics Conference (IPC), 2024)
We measure the temperature inside a proton exchange membrane (PEM) fuel cell with fiber Bragg gratings by incoherent optical frequency domain reflectometry (IOFDR). The results demonstrate the feasibility of installing an optical fiber inside a fuel cell and show proof of concept for temperature measurement

Fiber-Bragg-Grating Writing in Highly Nonlinear PM Fibers for Raman Fiber Lasers - Siekiera, Alexander; Engelbrecht, Rainer; Müller, E.; Schmauß, Bernhard (IEEE LEOS Winter Topicals Meeting Series, Innsbruck, Österreich, 12. - 14. Januar, 2009)
We describe the fabrication of flber-Bragg-gratings (FBG) in highly nonlinear polarization maintaining (PM) fibers with tight constraints concerning their spectral bandwidth and maximum reflectivity. The experimental setup for the inscription process and writing results are presented.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.fiberb

Fiber-modes and fiber-anisotropy characterization using low-coherence interferometry - Ma, Y. Z.; Sych, Denis; Onishchukov, Georgy; Ramachandran, S.; Peschel, Ulf; Schmauß, Bernhard; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2009)
An optical low-coherence interferometry technique has been used to simultaneously resolve the mode profile and to measure the intermodal dispersion of guided modes of a few-mode fiber. Measurements are performed using short samples of fiber (about 50 cm). There is no need for a complex mode-conversion technique to reach a high interference visibility. Four LP mode groups of the few-mode fiber are resolved. Experimental results and numerical simulations show that the ellipticity of the fiber core leads to a distinct splitting of the degenerate high-order modes in group index. For the first time, to the best of our knowledge, it has been demonstrated that degenerate LP11 modes are much more sensitive to core shape variations than the fundamental modes and that intermodal dispersion of high-order degenerate modes can be used for characterizing the anisotropy of an optical waveguide.
UnivIS-Import:2015-04-14:Pub.2009.nat.dphy.optik.1optik.fiberm

Fiber optic microbending sensors using modal power distribution analysis - Schmauß, Bernhard (1993)
lhft_intern.bib::thirty_years_LHFT_312

Fiber-optic Temperature Measurement Based on Fiber Bragg Gratings and Spontaneous Raman Backscattering in a Single Fiber - Köppel, Max; Werzinger, Stefan; Schmauß, Bernhard (CDT Sensor Day - Sensor Technologies and Applications, 2017)

Fiber sensor identification based on incoherent Rayleigh backscatter measurements in the frequency domain - Köppel, Max; Engelbrecht, Rainer; Werzinger, Stefan; Schmauß, Bernhard (International Conference on Optical Fiber Sensors (OFS), 2017)
In this work, a fiber identification method based on incoherent optical frequency domain reflectometry (IOFDR) measurements is introduced. The proposed method uses the characteristic interference pattern of IOFDR Rayleigh backscatter measurements with a broadband light source to unambiguously recognize different initially scanned fiber segments. The recognition is achieved by cross-correlating the spatially resolved Rayleigh backscatter profile of the fiber segment under test with a initially measured and stored backscatter profile. This profile was found to be relatively insensitive to temperature changes. It is shown that identification is possible even if the fiber segment in question is installed subsequent to 300m of lead fiber. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onl
lhft_intern.bib::Koeppel2017a

Fibre-Ended Photoacoustic Millimeter-Wave Detector - Brand, Hans; Stoeckel, B (1989)
lhft_intern.bib::thirty_years_LHFT_265

Field calculation in models of man in the near-field of antennas - Schaller, G; Engelbrecht, Rainer; Erb, J (IEEE, 1995)
For two examples the electromagnetic field is calculated inside and in the vicinity of properly modelled man in the near-field of antennas. The first example illustrates the SAR-distribution in a medical attendant near a deep hyperthermia system, whereas in the second example fields are calculated in a human head exposed to hand-held E-net phones. Both cases are investigated applying a 3-D field calculation program based on a finite integration algorithm.
lhft_intern.bib::thirty_years_LHFT_353

Field Calculation in Models of the Human Head Exposed to Hand-Held E-Net Phones - Schaller, Gerhard; Engelbrecht, Rainer; Erb, J. (26. Wissenschaftliche Tagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Röntgen Centenary Congress, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.fieldc_3

Field Calculation in Models of the Man in the Near-Field of Antennas - Schaller, Gerhard; Engelbrecht, Rainer; Erb, J. (1995 IEEE MTT-S International Microwave Symposium, 1995)
For two examples the electromagnetic field is calculated inside and in the vicinity of properly modelled man in the near-field of antennas. The first example illustrates the SAR-distribution in a medical attendant near a deep hyperthermia system, whereas in the second example fields are calculated in a human head exposed to hand-held E-net phones. Both cases are investigated applying a 3-D field calculation program based on a finite integration algorithm.
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.fieldc

Field Fluctuations in the Fresnel Zone of a Circular Focused Aperture in the Presence of Phase Errors - Aleksieieva, Anna; Dolzhikov, Vladimir (3rd European Conference on Antennas and Propagation (EuCAP2009), 2009)
In this paper the field fluctuation of a circular aperture focused in the Fresnel zone caused by the phase errors of the aperture distribution is investigated. Analytic expressions for the amplitude and phase dispersions of the radiation field and also for the coordinates of the maximum of the field intensity are given. The relation between the amplitude and phase dispersions and the statistical parameters of the phase errors and also the focal distance are investigated. The presented results illustrate that the performance of an antenna in its Fresnel zone is notably limited by the phase errors of the aperture distribution.
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.fieldf

Field Simulation for Interstitial Microwave Hyperthermia Using a Finite Integration Algorithm - Erb, J.; Engelbrecht, Rainer; Schaller, Gerd; Müller, R. G.; Sauer, R. (26. Wissenschaftliche Tagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) - Röntgen Centenary Congress, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.fields_8

Field Simulation for Interstitial Microwave Hyperthermia Using a Finite Integration Algorithm - Erb, J; Engelbrecht, Rainer; Schaller, G; Mueller, R; Sauer, R (1995)
lhft_intern.bib::thirty_years_LHFT_368

Field simulation of applicators for interstitial microwave hyperthermia - Schaller, G; Erb, J; Engelbrecht, Rainer; Seegenschmiedt, H (IEEE MTT-S International Microwave Symposium, 1995)
The electromagnetic field near clinically applied coaxial microwave applicators for interstitial hyperthermia is calculated using a finite integration algorithm program. Simulations of E-field and SAR distributions of different conventional applicators in a muscle phantom are presented and compared with measurements. The applied calculation method allows also design optimization and improvement of more sophisticated applicator types, e.g. those using a triaxial techniq
lhft_intern.bib::schaller95a

Field Simulation of Dipole Antennas for Interstitial Microwave Hyperthermia. - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard (IEEE Transactions on Microwave Theory and Techniques, 1996)
The electromagnetic field of dipole antennas for interstitial microwave hyperthermia is investigated using a finite integration algorithm program. The numerical method is applied to conventional, clinically used applicators and is also used for the improvement and optimization of sophisticated applicators, e.g., in a triaxial technique. Simulations of the frequency dependent impedance match, the E-fleld and the specific absorption rate (SAR) distribution of different applicators immersed in a muscle phantom are presented and compared with measurements. Moreover, results for arrays of two and four applicators are given. The field simulation allows one to study the effects at the various discontinuities of the applicator-catheter-tissue system and gives a better understanding of known phenomena. © 1996 IEEE.
UnivIS-Import:2015-03-05:Pub.1996.tech.IE.LEH.fields

Field Simulation of Interstitial Microwave Applicators - Engelbrecht, Rainer; Schaller, Gerhard (Med. Phys. 22(6), 905, AAPM 37^th Annual Meeting, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.fields

Field Simulation of Microwave Applicators for Interstitial Hyperthermia - Erb, J; Engelbrecht, Rainer; Schaller, G (1995)
lhft_intern.bib::thirty_years_LHFT_376

Field Simulation of Microwave Applicators for Interstitial Hyperthermia - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard (Meeting of the Europ. Soc. Hyperthermia Oncology ESHO, 1995)
The electromagnetic field near clinically applied coaxial microwave applicators for interstitial hyperthermia is calculated using a finite integration algorithm program. Simulations of E-field and SAR distributions of different conventional applicators in a muscle phantom are presented and compared with measurements. The applied calculation method allows also design optimization and improvement of more sophisticated applicator types, e.g. those using a triaxial technique.
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.fields_2

Field Simulation of Microwave Applicators Used for Inasive Hyperthermia Treatments - Technical and Clinical Perspectives - Erb, J.; Engelbrecht, Rainer; Schaller, Gerhard (Proceedings of the 7th International Congress on Hyperthermic Oncology, 1996)
UnivIS-Import:2015-04-16:Pub.1996.tech.IE.LEH.fields_8

Filter-based Segmentation of Automotive SAR Images - Hoffmann, Marcel; Noegel, Theresa; Schüßler, Christian; Vossiek, Martin; Schütz, Martin; Gulden, Peter (2022 IEEE Radar Conference, 2022)
This paper presents an approach to the segmentation of automotive synthetic aperture radar (SAR) images generated with a state-of-the-art multiple-input multiple-output frequency modulated continuous wave radar. Due to the very high image resolution and large signal-to-noise ratio, it is possible to directly distinguish different free spaces, extended objects, or target areas, such as walls or cars, and point-like targets, including posts and trees. The latter are detected using a constant false alarm rate algorithm, whereas free spaces and target areas are segmented by using Otsu's method after morphologically processing the SAR image. With this simple, filter-based segmentation, the perception of the vehicle's environment can be improved without complex post-processing that is typically required in standard radar gridmaps.<br
Keywords: radar imaging; automotive radar; FMCW; SAR; image segmentation

Fin-line PIN-diode switches for mm-waves with extremely high isolationand short switching time - Callsen, H; Schmidt, Lorenz-Peter (ibid, 1987)
lhft_intern.bib::Schmidt16

Flexible low-loss dielectric waveguides for THz frequencies with transitions to metal waveguides - Hofmann, Arnd; Hörster, Eva; Weinzierl, Jochen; Schmidt, Lorenz-Peter; Brand, Hans (33rd European Microwave Conference, EuMC 2003, 2003)
A flexible low-loss dielectric waveguide system for sub-millimetre wave frequencies up to 600 GHz is presented, with measured attenuation values shown at 300 GHz. Mode transformers for an accurate and reproducible transition to metal waveguides have been investigated and improved. © 2003 EUMA.

Flexible Polymer Shape Sensor Based on Planar Waveguide Bragg Gratings - Rosenberger, M.; Pauer, H.; Girschikofsky, M.; Woern, H.; Schmauß, Bernhard; Hellmann, R. (IEEE Photonics Technology Letters, 2016)
A newly developed concept for a miniaturized optical shape sensor is demonstrated. The sensor consists of a flexible polymer bending beam with two integrated optical waveguide Bragg gratings spatially staggered to each other. We report on the basic layout and the fabrication process and characterize the fundamental sensing response by an elaborate testing scheme. The polymer shape sensor reveals a pronounced spectral shift of the Bragg wavelength of several nanometers upon deformation with a distinct directionality. In conjunction with an undiscernible hysteresis, these results highlight the general applicability of the polymer Bragg grating-based bending beam as a shape senso
lhft_intern.bib::rosenberger2016flexible

Fluorescence Lifetime Measurements of a Trapped Microparticle in a Hollow-Core Fiber for Remote Temperature Sensing with High Spatial Resolution - Freitag, Jasper; Köppel, Max; Sahil, Mohammad; Joly, Nicolas; Schmauß, Bernhard (Optical Fiber Communication Conference (OFC) 2025, 2025)
Fluorescence lifetime measurements of trapped microparticles in hollow-core fibers can probe temperature with high sensitivity. We use coherent optical frequency domain reflectometry to demonstrate remote flying particle temperature measurements with sub-mm spatial resolutio

Flying Particle Thermosensor in Hollow-Core Fiber Based on Fluorescence Lifetime Measurements - Freitag, Jasper; Köppel, Max; Romodina, Maria N.; Joly, Nicolas; Schmauß, Bernhard (IEEE Journal of Selected Topics in Quantum Electronics, 2023)
Keywords: frequency-domain fluorescence lifetime; hollow-core fiber; optical trapping; flying particle temperature sensor

FM-ICW monopulse radar sensor - Schmidt, Lorenz-Peter; Jester, R; Kadisch, G (Military Microwave Conference, 1990)
lhft_intern.bib::Schmidt20

Forschungsverbund Lasertechnologie Erlangen (FLE) - Brand, Hans (1989)
lhft_intern.bib::thirty_years_LHFT_261

Four-port on Wafer Measurement of Coupled Transmission Lines on LTCC - Ziegler, Christof; Nisznansky, Martin; Schmidt, Lorenz-Peter; Hocke, Ralf; Wohlgemuth, O. (Proceedings of IMAPS Conference and Exhibition on Ceramic Interconnect Technology, 2003)
The measurement results of coupled transmission lines on LTCC multilayer substrates are presented in this paper. The S-parameters of 4-port devices have been measured using a newly developed topology of a multiport vector network analyzer (VNA). A method for a multiport calibration based on multiple 2-port TRL-calibration routines is presented. The procedure has been developed for the use of a wafer probe station with coupled probe tips in combination with the 4-port VNA. To extract information about the capabilities of the measurement system, the measured data of the coupled microstrip lines on LTCC are compared to the results of a numerical circuit simulation of these lines. The measured single-ended S-parameters were transformed to a modal description by matrix transformation, describing the characteristics of the measured devices at common-mode or differential-mode stimulus. The results of the measurements and simulations will be discussed.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.fourpo
Keywords: Calibration; Modal S-parameters; Multiport; Network analysis; TRL

FOV-based model predictive object tracking for quadcopters - Snobar, Fadi; Reinhard, Johannes; Huber, Hartwig; Hoffmann, Marcel; Stelzig, Michael; Vossiek, Martin; Graichen, Knut (9th IFAC Symposium on Mechatronic Systems (Mechatronics 2022), 2022)

Free space optical communication with spatial diversity based on orbital angular momentum of light - Raoof Mehrpoor, Gilda; Safari, Majid; Schmauß, Bernhard (Optical Wireless Communications (IWOW), 2015 4th International Workshop on, 2015)
In this paper, the use of optical beams carrying orbital angular momentum (OAM) is proposed to provide spatial diversity gains for free space optical communication links degraded by atmospheric turbulence. We show that transmitted beams carrying sufficiently separated OAM modes experience highly uncorrelated turbulence effects. Furthermore, the outage probability analysis confirms that spatial diversity gain is achievable using the proposed technique without requiring the deployment of multiple apertures which is necessary for traditional spatial diversity scheme
lhft_intern.bib::mehrpoor2015free

Frequency Extension Method for Multirate Radar Target Simulation Systems - Körner, Georg; Birkenhauer, Christoph; Stief, Patrick; Carlowitz, Christian; Vossiek, Martin (14, 2022)
Radar target simulation is an important tool for testing and characterizing radar systems. It was shown before, that multi rate radar target simulators allow for highly accurate emulation of moving targets. These multi rate systems are a special case of digital radio frequency memory systems. By using different sampling clocks in the ADCs and DACs, moving targets can be simulated with outstanding realistic behavior, since this multirate system mimics the behavior of the continuous target distance changes perfectly. In this paper, we demonstrate for the first time how the frequency range of the multirate digital target emulation can be extended. We want to apply sub-Nyquist sampling techniques combined with the multirate technique and analyze its effect. It is shown that sub-Nyquist sampling does not change the signal properties; rather, the signals are downconverted via the sampling process, which enables direct coverage of higher frequency bands. This reduces the cost and complexity of hardware designs for multirate radar target simulation compared to previously demonstrated mixer-based down-conversion. We successfully demonstrate a frequency range extension of the baseband system by a factor of more than fiv
Keywords: radar target simulation; FMCW; DRFM; OFDM

Frequency-sweep linearization for FMCW sensors with high measurement rate - Pichler, Markus; Stelzer, Andreas; Gulden, Peter; Seisenberger, Claus; Vossiek, Martin (IEEE/MTT-S International Microwave Symposium Digest, 2005)
In certain object surface distance measurement applications where contactless and robust estimates are required, microwave frequency modulated continuous wave sensors are the solution of choice. High linearity of transmitted frequency over time is a prerequisite for accurate results and poses a challenge, if high measurement rates are to be achieved simultaneously. This paper presents a novel method for sweep linearization in phase-locked-loop-based frequency synthesizers by determining the instantaneous output signal phase and -error directly within the synthesizer. The proposed method is compared to a conventional voltage predistortion linearization technique. © 2005 IEEE.
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.freque
Keywords: Chirp radar; Frequency synthesizers; Phase locked loops; Phase measurement

Frequency tuning of microwave filter at 60 GHz by laser ablation - Siekiera, Alexander; Engelbrecht, Rainer; Bauer, Robert H.; Rehner, Robert; Schmauß, Bernhard (Frequenz, 2009)
The transfer characteristic of microwave filters realized as microstrip circuits is depending on geometrical properties of the structured conducting layers as well as on the material properties of the used substrate. Due to variations of material properties and manufacturing tolerances a certain deviation of target to realized transfer function has to be tolerated. In this article a method for the subsequent tuning of filter characteristics using an excimer laser is presented. By laser ablation of the metal thin film layer, material removal with a minimum size in the range of 5 μm is achieved.
UnivIS-Import:2015-03-09:Pub.2009.tech.IE.LEH.freque
Keywords: Excimer laser ablation; Microstructuring; Microwave filter tuning

Frontend MMICs for millimeter wave frequencies up to 100 GHz - Adelseck, B; Schmidt, Lorenz-Peter; Dieudonne, J; Guettich, U; Klaassen, A; Coloquhoun, A (Military Microwave Conference, 1992)
lhft_intern.bib::Schmidt25

Full D-Band GaN Power Amplifier MMIC and Waveguide Module - Cwiklinski, Maciej; Riedmann, Nico; Ziegler, Robert; Vossiek, Martin; Bruckner, Peter; Schwantuschke, Dirk; Mikulla, Michael (2024 19th European Microwave Integrated Circuits Conference, EuMIC 2024, 2024)
In this article, we present a gallium nitride (GaN) power amplifier (PA) monolithic microwave integrated circuit (MMIC) and waveguide module that cover the full D-band (110-170 GHz) with a state-of-the-art performance. On-wafer measurements of the balanced ten-stage GaN PA show a small-signal gain of more than 13 dB over the full D-band and a peak output power of 22.6 dBm at 160 GHz. A two-way waveguide module delivers more than 18.5 dBm of output power over the full D-band with a peak of 25 dBm at 120 GHz. To the best of our knowledge, the reported amplifiers show the highest output power within GaN-based circuits beyond 140 GHz. This is also the first demonstration of GaN PAs covering the full D-band.
CRIS-Team Scopus Importer:2024-12-13
Keywords: Broadband; D-band (110-170 GHz); gallium nitride (GaN); high-electron-mobility transistor (HEMT); monolithic microwave integrated circuit (MMIC); power amplifier (PA); waveguide module

Full polarimetric THz imaging system in comparison with infraredthermography - Nezadal, Martin; Schür, Jan; Schmidt, Lorenz-Peter (11th European Conference on Non-Destructive Testing, 2014)
lhft_intern.bib::NezadalECNDT2014

Fully Electronic Active E-Band Personnel Imager with 2 m^2 Aperture - Ahmed, Sherif Sayed; Genghammer, Andreas; Schießl, Andreas; Schmidt, Lorenz-Peter (IEEE MTT-S International Microwave Symposium 2012 (IMS 2012), 2012)
The demand on advanced personnel screening systems led to the development of several active and passive imagers. Among them, active multistatic imaging ensures high image quality and allows fully electronic screening. An active E-band imager is introduced in this paper, which operates in real-time and delivers images of 30-dB dynamic range. Imaging of humans is achieved by optimizing the acquisition time using a dedicated digital signal processing solutio
lhft_intern.bib::Ahmed2012b

Fully Polarimetric Short-Range Imaging Radar - Adametz, Julian (13th European Radar Conference (EuRad), Workshop on Short Range mmWave Imaging Systems, 2017)
lhft_intern.bib::Adametz17b

Funkbasierte 3D-Lokalisierung von Tieren zur Verhaltensanalyse im Innen- und Außenbereich - Ebelt, Randolf; Millner, Hendrik; Hoffmann, Gundula; Vossiek, Martin (Radio Techniques and Technologies for Commercial Communication and Sensing Applications, RadioTecC 2009, 2009)
UnivIS-Import:2015-04-16:Pub.2009.tech.IE.LEH.funkba

Funkbasierte Netzwerk-zu-Netzwerk-Ortung zur Bestimmung der Position und Orientierung von Fahrzeugen - Ebelt, Randolf; Vossiek, Martin (FAM-Workshop Navigation und Lokalisierung, 2011)
lhft_intern.bib::Ebelt2011a

Funkortung in Gebäuden - Vossiek, Martin (Radio Techniques and Technologies for Commercial Communication and Sensing Applications, RadioTecC 2004, 2004)
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.funkor

Funkortungs- und Identifikationssystem fuer Industrieanwendungen - Vossiek, Martin (Technologie-Informationen niedersächsischer Hochschulen, 2006)
lhft_intern.bib::Vossiek2006a

Funksysteme zur Ortung von Werkzeugen und Transportmitteln in der Produktion - Kirsch, Fabian; Vossiek, Martin (Funklokalisierung – sicher, schnell und genau, oeffentliche Diskussionssitzung des ITG-Fachausschuss 7.2, 2010)
lhft_intern.bib::Kirsch2010

Fusion of FMCW Secondary Radar Signal Beat Frequency and Phase Estimations for High Precision Distance Measurement - Max, Stephan; Vossiek, Martin; Gulden, Peter (5th European Radar Conference (EuRAD 2008), 2008)
The accuracy of a radar operating in a multipath environment or in presence of strong clutter noise is mainly limited by the radar signal bandwidth. In the actual paper a phase evaluation concept is introduced that allows for the estimation of the distance of a moving target with mm accuracy even under the above mentioned conditions. The concept is based on an algorithm that combines beat frequency and phase acceleration estimations. The paper will discuss the theoretical background of the approach and the performance of the concept will be illustrated by measurement results of a 5.8 GHz secondary radar system. © 2008 EuMA.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.fusion

Fuzzy logic applied to an intelligent ultrasonic distance sensor. Unterdrückung von Mehrfachechos mittels Fuzzy-logik-Auswertung bei der Entfernungsmessung mit einem Ultraschallsensor. - Eccardt, P.-C.; Vossiek, Martin; Magori, V. (Europ. Congress on Intelligent Techniques and Soft Computing, 1995)
UnivIS-Import:2015-04-16:Pub.1995.tech.IE.LEH.fuzzyl

GaAs MMIC based components and frontends for millimeterwave communication and sensor systems - Dämbkes, H; Adelseck, B; Schmidt, Lorenz-Peter; Schroth, J (Microwave Systems Conference, 1995)
In the millimeter wave region several communication and sensor systems are emerging which presently are served only by III/V based technologies. First sensor systems of relevant volume market are tested at 76 GHz for automotive sensors, with other systems operating at 60 GHz and 94 GHz. For mm-wave communication systems volume applications arise at 38 GHz for the interconnection of PCN cells. This paper describes GaAs based technologies and components which are available to serve the requirements of mm-wave communication sensor systems up to 80 GH
lhft_intern.bib::Schmidt34

GaAs Schottky diode fabrication for THz-frequency mixer applications - Cojocari, O.; Biber, Stephan; Mottet, B.; Hartnagel, H.; Schmidt, Lorenz-Peter (Proc. the 28th Workshop on Compound Semiconductor Device and Integrated Circuits held in Europe, Smolenice Castle, Slovakia, 17-19 May, 2004)
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.gaassc

Gasanalyse im CO_2-Laser mittels Diodenlaser-Spektrometrie - Engelbrecht, Rainer (Friedrich-Alexander-Universität Erlangen-Nürnberg, 2001)
UnivIS-Import:2016-07-26:Pub.2001.tech.IE.LEH.gasana

Gasanalyse im CO_2-Laser mittels Diodenlaser-Spektrometrie - Engelbrecht, Rainer (Didacta Verlag, 2002)
UnivIS-Import:2015-04-02:Pub.2002.tech.IE.LEH.gasana

Gas Discharge Impedance and Transmission Line Voltages in a RF Excited CO₂ Slab Laser - Engelbrecht, Rainer; Schulz, R.; Seibert, Günter; Hagen, J.; Schmidt, Lorenz-Peter (Frequenz, 2005)
The impedance of a RF excited gas discharge slab-type CO 2 laser is determined experimentally. The electrode pair is treated as a lossy transmission line to calculate the voltage distribution along the electrodes. Optimum inductances for homogenization of the gas discharge are derived and compared with experimental results.
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.gasdis
Keywords: Carbon dioxide; Lasers; Lossy transmission line; RF gas discharge

Generation of 3D Functional Structures for High- Frequency Applications by Printing Technologies - Ankenbrand, Markus; Scheetz, Matthias; Franke, Jörg; Lomakin, Konstantin; Sippel, Mark; Gold, Gerald; Helmreich, Klaus (2018 13th International Congress Molded Interconnect Devices (MID), 2018)
The following topics are dealt with: polymers; adhesion; rapid prototyping (industrial); mechatronics; aerosols; injection moulding; moulding; three-dimensional printing; metallisation; electrical resistivit

Generation of RF Structures on Additively Manufactured Substrates by Printed Electronics and Laser Structuring - Ankenbrand, Markus; Panusch, David; Utsch, Daniel; Banea, Kevin; Ehrngruber, Michael; Gold, Gerald; Helmreich, Klaus; Franke, Jörg (Proceedings of the SMTA Pan Pacific Microelectronics Symposium 2023, 2023)
In this work, printed electronics and laser processes are utilized to generate radio frequency (RF) structures for the X-band on additively manufactured substrates. The substrates are generated by Fused Filament Fabrication (FFF) with various materials. Conductive structures are applied with the processes Piezojet, Nanojet and Laser Direct Structuring (LDS). Piezojet is a drop-on-demand inkjet process that can print a wide range of inks and pastes with viscosities up to 200,000 mPas. Typical line widths are in the range of 300 - 500 μm. Nanojet uses ultra-sonic atomization to create an aerosol from a functional ink. In the nozzle, the aerosol is focused by an additional gas flow, which enables line widths as fine as 20 μm. Both Piezojet and Nanojet require a post-treatment step to dry or sinter the applied inks in order to achieve full conductivity. The LDS process works with a laser-activatable additive that is compounded into the material. Circuit tracks are generated by laser-scanning the layout on the substrate surface. The areas activated in this process are then metallized in an electroless plating process to achieve conducting paths. Moreover, the LDS-laser can also be used to smoothen the 3D-printed substrate surfaces and for sintering and trimming the circuits printed with Piezojet and Nanojet. In order to evaluate the different process and material combinations, the following coplanar structures are printed on additively manufactured substrates: Transmission line sections, a bandpass and a resonator. A network analyzer is used to measure the scattering parameters of the printed structures. With the measured magnitude and phase together with the geometry of the lines, an estimation for the relative permittivity εr can be obtained. This parameter is later used in the design process of an additively manufactured helix antenna. This antenna type offers a small form factor in combination with high gain and bandwidth, while radiating a signal of circular polarization. Many RF applications like satellite communication or radar imaging rely on circular polarized antennas [1,2]. The helix antenna is manufactured with the above-described processes in a 5-axis motion syste
Keywords: Additive Manufacturing; Printed Electronics; Microwave Technology; Mechatronic Integrated Devices; Helix antenna; X-band

Global navigation satellite systems in passive surveillance applications - Wachtl, Stefan; Koch, Volker; Schmidt, Lorenz-Peter (ESAV'14 - Enhanced Surveillance of Aircraft and Vehicles International Workshop, 2014)
The possibility to detect and analyze multipath signals of global navigation satellite systems (GNSS) caused by aircrafts is an attractive basis for the development of a passive surveillance sensor. Due to the fact that the received signal strength of global navigation satellite systems on earth surface is very low and the radar cross sections (RCS) of an aircraft strongly varies with the illumination and observation angles, such a passive sensor will offer a high probability of detection with respect to a hemispheric field of view preferably in a multistatic sensor array configuration. In this work measurements with a single sensor and considerations about possibilities to range an aircraft with a multistatic sensor array are presente
lhft_intern.bib::Wachtl2014

Greencard - Eine Loesung? - Brand, Hans (Forschung & Lehre : alles was die Wissenschaft bewegt, 2000)
lhft_intern.bib::brand00a

Group delay measurements of multicore fibers with correlation optical time domain reflectometry - Azendorf, Florian; Dochhan, Annika; Spinty, Florian; Lawin, Mirko; Schmauß, Bernhard; Eiselt, Michael (International Conference on Transparent Optical Networks, 2020)
Several multi-core fibers (MCF) were characterized using Correlation Optical Time Domain Reflectometry (C-OTDR) in terms of propagation delay and polarization mode dispersion (PMD). The results show that the propagation delay in the cores depends on the position of the core in the fiber and that the differential delay between the cores varies with temperature.
CRIS-Team Scopus Importer:2020-10-23
Keywords: Fiber characterization; Multi-core fiber; Network monitoring; Optical time domain reflectometry

Growth rate of pressure induced triolein crystals - Roßbach, Andre; Bahr, Leo; Gäbel, Sebastian; Bräuer, Andreas; Wierschem, Andreas (Journal of the American Oil Chemists Society, 2019)
In pressure-induced crystal growth of triolein from melt at pressures up to 300 MPa and at temperatures between 283.16 and 293.16 K, we can distinguish three different crystal morphologies. Raman spectroscopy indicates that they are related to different polymorphic structures. Switching from the most stable to a less-stable structure implies a jump in the growth rate to a maximum value. As pressure increases, the growth rate decreases indicating that the growth is transport limited. Measurements at different temperatures show that the growth rate is mainly governed by pressure. In a certain parameter range, we observe crossnucleation to crystals with a higher growth rate. These crystals have a Raman fingerprint not yet described in the literature.<br
Keywords: Pressure-induced crystallization; Growth rate; Polymorphism; Cross-nucleation; Transport-limited growth; Triolein

Grundlagen der Elektrotechnik 3 - Netzwerke, Foundations of Electrical Engineering 3 - Network Theory - Schmidt, Lorenz-Peter; Schaller, Gerhard; Martius, Siegfried (Pearson Education, Munich, Jan., 2006)
UnivIS-Import:2015-04-02:Pub.2006.tech.IE.LEH.grundl

Grundlagen der Mikrowellensensorik - Vossiek, Martin (Tutorial, Radar and Communication, RADCOM 2005, Fachmesse - Workshop - Entwicklerforum, 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.grundl

Grundlagen des Lasers - DGM- Praktikum-Textbuch Bayer - Brand, Hans (1995)
lhft_intern.bib::thirty_years_LHFT_390

Grundlagen und Anwendung der Laser-Koagulation im Gastrointestinaltrakt - Reidenbach, H; Fruehmorgen, P; Bodem, F; Brand, Hans; Demling, L (1979)
lhft_intern.bib::thirty_years_LHFT_100

Hardware Realization of a 2 m x 1 m Fully Electronic Real-Time mm-WaveImaging System - Schiessl, A.; Genghammer, A.; Ahmed, S. S.; Schmidt, Lorenz-Peter (EURSAR 2012, 2012)
A first generation of active mm-wave imaging devices is nowadays commercially available for industrial and security applications. Mostly, these systems use mechanical scanning to reduce channel count. The availability of state-of-the-art semiconductor technology enables reliably building high-channel-count fully electronic mm-wave imaging systems at E-Band frequencies, including parallel signal processing. Without the need for mechanical scanning, true real-time operation becomes possible. This work describes a prototype of such an imaging system for personnel screening applications. For the first time, hardware that is capable of capturing full 2 m × 1 m images of living persons in the 80 GHz region in real-time is demonstrated. An overview of the imaging system is given including detailed hardware description. The measurement flow is explained and the underlying link budget is derived.
lhft_intern.bib::Schiessl2012

Heat, Vibration, Dust, Salt spray, Weather - Taking Wireless Positioning to the Extreme - Millner, Hendrik; Gulden, Peter; Roehr, Sven; Christmann, Mark; Vossiek, Martin (IEEE Radio Wireless Week 2013, 20-23 Jan., 2013)
There are lots of local positioning systems available for indoor applications, partly even for outdoor use. Many of them rely on a rather clean environment which does not interfere in their measurements too much. Industrial environments, in-or outdoors, often do not meet these requirements. The positioning applications here are surrounded by dirt, dust and vibrations. The number of local positioning systems being able to perform properly here at all times is limited to such not dependent on optical or sonic measurements. Local secondary radar systems proved to be a reliable source of distance and position measurements, even in harsh environments. This paper examines a few use cases and depicts the performance of local positioning radar systems there. © 2013 IEE
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.heatvi
Keywords: Distance measurement; Position measurement; Radar applications; Wireless sensor networks

Hemocompatibility of EpoCore/EpoClad photoresists on COC substrate for optofluidic integrated Bragg sensors - Hessler, Steffen; Rueth, M.; Sauvant, C.; Lemke, H. -D.; Schmauß, Bernhard; Hellmann, R. (Sensors and Actuators B-Chemical, 2017)
We report on the hemocompatibility properties of EpoCore/EpoClad UV-structurable epoxy resins in combination with a TOPAS® cyclic olefin copolymer substrate for potential application as an optofluidic biosensor chip. For comprehensive hemocompatibility tests human blood is directly exposed to layers of the different chip materials up to 3 h. Counts in white blood cells, red blood cells and platelets as well as hemolysis and concentration of thrombin/antithrombin complex (TAT), of complement fragment (C5a) and heparin are determined. Our results attest TOPAS and the epoxy resins high hemocompatibility properties. Subsequently, an optofluidic chip fabrication concept with integrated Bragg grating sensors is suggested. Bragg gratings are directly inscribed into rectangular EpoCore waveguides on TOPAS 6017 substrate by coherent phase mask illumination. UV-structured EpoClad resist serves both as waveguide cladding and microfluidic channel network. In evanescent field refractive index sensing experiments sensitivities up to 76.9 nm/RIU and a maximum refractive index resolution of 1.3·10−5 are achieved by detecting multimode Bragg reflection

Herstellung und Charakterisierung eines extrinsischen faseroptischen Elementarsensors zur Temperaturmessung - Schmauß, Bernhard; Trautner, R.; Shamonin, M. (Technisches Messen, 2008)
UnivIS-Import:2015-03-09:Pub.2008.tech.IE.LEH.herste
Keywords: ISSN x

Heterostructure Equivalence of Step-Recovery Diodes for Ballistic and Diffusive Electron Resonance - a New Concept for THz Signal Generation - Hartnagel, H.; Schmidt, Lorenz-Peter; Nicolae, B.; Oprea, I.; Schoenherr, D.; Ong, D.; Schür, Jan; Ruf, Marcel (Proceedings of 33rd international Conference on Infrared, Millimeter and Teherahertz Waves, 2008)
A heterostructure equivalent to the well-known step recovery diode principle, arranged as a double structure gives a new nonlinear device for highly efficient harmonic THz signal generation. Like in the case of step recovery diodes, these devices exhibit promising performance especially for the generation of higher order harmonics. Theoretical and experimental results will be presented. ©IEEE.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.hetero

HF-Components for Harsh Environments using Investment Casting with Additive Manufacturing - Panusch, David; Gold, Gerald (WISEE -THE IEEE WIRELESS IN SPACE AND EXTREME ENVIRONMENTS CONFERENCE, 2024)
Recently, investment casting has been proposed for the production of microwave components. This novel manufacturing method combines the advantages of additive manufacturing with a robust all-metal structure. This makes it particularly suitable for aerospace, maritime and other applications where durability, temperature range and stiffness are required. In this talk, casted waveguides with different metal alloys will be compared to their conventional equivalents, i.e. milled split blocks. Through and resonator measurements were performed to determine the effective conductivity, which includes not only the conductivity but also the effect of surface roughness. In addition, the surface profiles of the samples were measured. Future applications could benefit from this fabrication approach with few overall design constraints. However, morphological optimization of the components, e.g. structural reinforcements, is essential for mechanical stability, where the trade-off between weight, electrical performance and stiffness must be considered. This is demonstrated using a corrugated horn antenna array for E-band applications.<br

Hierarchical Beam Alignment in Single-User MIMO Single-Carrier Frequency Division Multiple Access Terahertz Communication Systems - Wu, Yifei; Koch, Johannes; Vossiek, Martin; Gerstacker, Wolfgang (2021 IEEE International Conference on Communications Workshops, ICC Workshops 2021 - Proceedings, 2021)
Single-carrier frequency division multiple access (SC-FDMA) is a promising technique for high data rate Terahertz (THz) communications in future beyond 5G systems. Beam alignment (BA) is considered as a mandatory solution to establish a reliable communication link in SC-FDMA THz communication. However, existing BA methods introduce a large latency in searching for the optimal beam. In this paper, we propose a multi-armed bandit algorithm referred to as hierarchical beam alignment (HBA) for single-user SC-FDMA THz systems to reduce the beam alignment latency. HBA utilizes a hierarchical structure in the adopted codebook and the prior knowledge regarding the frequency-selective fading of the channel to speed up the BA process. Both theoretical analysis and simulation results illustrate that HBA converges to the optimal beam with high probability. The latency introduced by HBA is significantly lower compared to an exhaustive search method.
CRIS-Team Scopus Importer:2021-08-27
Keywords: Beam alignment; indoor Terahertz communication; SC-FDMA

Hierarchical beam alignment in SU-MIMO terahertz communications - Wu, Yifei; Koch, Johannes; Vossiek, Martin; Gerstacker, Wolfgang (ITU Journal: ICT Discoveries, 2021)
Single-Carrier Frequency Division Multiple Access (SC-FDMA) is a promising technique for high data rate indoor Terahertz (THz) communications in future beyond 5G systems. In an indoor propagation scenario, the Line-Of-Sight (LOS) component may be blocked by the obstacles. Thus, efficient THz SC-FDMA communications require a fast and reliable Beam Alignment (BA) method for both LOS and Non-Line-Of-Sight (NLOS) scenarios. In this paper, we first adopt the hierarchical discrete Fourier transform codebook for LOS BA, and introduce the hierarchical k-means codebook for NLOS BA to improve the beamforming gain. Simulation results illustrate that the hierarchical DFT codebook and the hierarchical k-means codebook can achieve the beamforming gain close to that of the maximum ratio transmission in LOS and NLOS cases, respectively. Based on these two codebooks, we propose a Multi-Armed Bandit (MAB) algorithm named Hierarchical Beam Alignment (HBA) for single-user SC-FDMA THz systems to reduce the BA latency. HBA utilizes a hierarchical structure in the adopted codebook and prior knowledge regarding the noise power to speed up the BA process. Both theoretical analysis and simulation results indicate that the proposed BA method converges to the optimal beam with high probability for both the hierarchical DFT codebook and the hierarchical k-means codebook in the LOS and NLOS scenarios, respectively. The latency introduced by HBA is significantly lower when compared to an exhaustive search method and other MAB-based methods.
Keywords: Beam alignment; codebook design; SC-FDMA; SU-MIMO; terahertz communications

High-Accuracy 3D SAW RFID Tag Localization Using a Multi-Antenna Mobile Robot Based Synthetic Aperture Approach - Caldero, Pau; Gareis, Matthias; Vossiek, Martin (2020 50th European Microwave Conference, EuMC 2020, 2021)
Asset localization for inventory and management applications can benefit from the characteristics of surface acoustic wave (SAW) radio frequency identification (RFID), adding valuable information in Industrial Internet of Things (IIoT) ecosystems. An innovative approach using this technology combined with a multi-channel interrogation hardware integrated on a mobile robot platform under indoor conditions is studied in this work. With this novel system advance, SAW RFID tags can be localized in three dimensions within centimeter accuracy. The system concept and algorithms are described in detail in this paper. Furthermore, the performance in terms of localization accuracy is evaluated theoretically and experimentally and a root mean square error of 1.6 cm is achieved.
CRIS-Team Scopus Importer:2021-03-05
Keywords: 3D localization; RFID; SAR; SAW

High-Accuracy Localization and Calibration for 5-DoF Indoor Magnetic Positioning Systems - Hehn, Markus; Sippel, Erik; Carlowitz, Christian; Vossiek, Martin (IEEE Transactions on Instrumentation and Measurement, 2018)
Magnetic local positioning systems are a well-suited candidate for reliable indoor positioning systems, as they are robust against blocking by dielectric materials like walls or people. The system presented in this paper is implemented with a one-axis magnetic transmitter and several three-axis field sensors connected to a complete sensor network. Unfortunately, the performance of the system is severely impaired by field sensor nonidealities such as magnetic coupling of the sensor coils, coil misalignment, field sensor rotation, and unsynchronized sampling. In this paper, the overall field sensor impairments and an additive Gaussian noise model superposing the magnetic field are mathematically described. Then, a novel calibration scheme for the overall field sensor nonidealities is presented. Furthermore, a statistically optimal localization procedure coping with the field sensor nonidealities is developed. The proposed novel localization and calibration algorithms are demonstrated in a common office environment with a size of 7 m x 5 m x 3 m. Thereby, the calibration impressively reduces the position root-mean-square error (RMSE) from 46.8 to 10.6 cm and the angle RMSE from 24.8° to 6.1
Keywords: Magnetic resonance; Coils; Calibration; Robot sensing systems; Couplings; Magnetic domains; Magnetoacoustic effects; Calibration; field sensor; indoor navigation; localization; magnetic fields; magnetic local positioning

High bit-rate MIMO transport over multimode fiber - Bulow, H.; Franz, B.; Al Hashimi, Hussein Husham Jasim; Schmauß, Bernhard (OptoeElectronics and Communications Conference (OECC), 2011)
In lab experiment an increase of the receiver number enables stable direct-detection MIMO transmission over GI-MMF. For coherent detection MIMO which paves the way to higher capacity, different options for input / output couplers, processing schemes and coding are discussed.
lhft_intern.bib::Bulow2011

Higher Order Pulse Modulators for Time Domain Chipless RFID Tags with Increased Information Density - Mandel, Christian; Schubler, Martin; Nickel, Matthias; Kubina, Bernd; Jakoby, Rolf; Pöpperl, Maximilian; Vossiek, Martin (European Microwave Week, 2015)
lhft_intern.bib::Key2013

High-Frequency Modeling of Coplanar Waveguides Including Surface Roughness - Gold, Gerald; Lomakin, Konstantin; Helmreich, Klaus; Arz, Uwe (Advances in Radio Science, 2019)
An existing analytical transmission line model to describe propagation properties of coplanar waveguides including dispersion and radiation effects was extended to take into account surface roughness of conductor traces. The influence of parasitics is successively included in the simulation and compared to measurements. The device under test (DUT) was fabricated on an Al2O3 wafer. A metal and ceramic chuck was utilized during measurements up to 120 GHz. The extended model is then capable of precisely predicting propagation properties in a wide frequency range and can now be used for calibration purposes like the development of uncertainty budget

Highly Integrated 4-32-GHz Two-Port Vector Network Analyzers for Instrumentation and Biomedical Applications - Nasr, Ismail; Nehring, Johannes; Schütz, Martin; Dietz, Marco; Nasr, Ismail; Aufinger, Klaus; Weigel, Robert; Kissinger, Dietmar (IEEE Transactions on Microwave Theory and Techniques, 2016)
This paper addresses the miniaturization of microwave vector network analyzers (VNAs) and the future vision of the VNA on a chip. Therefore, a highly integrated two-port VNA with a multioctave bandwidth from 4 to 32 GHz is presented. The proposed system is based on a fully integrated radio-frequency frontend consisting of a two-port stimulus, a four-channel heterodyne receiver, and a wideband testset. The testset is comprised of on-chip multisection directional couplers. The chip is operated inside a hardware demonstrator using a 16-term calibration procedure. The measurement of arbitrary devices under test is in excellent agreement with commercial measurement equipment and showed a mean deviation from the reference measurement of 0.17 dB and 1.29° regarding the forward transmission of a coaxial 30-dB attenuator. The system and receiver dynamic ranges are 44-77 and 82-101 dB at a resolution bandwidth of 100 kHz over the full system bandwidth. The measurements are highly repeatable and are robust against drift over time. As a proof of concept, the developed integrated network analyzers are utilized in a biomedical sensing scenario with an external and an on-chip sensor. Both approaches showed good sensitivity regarding the mixture ratio of binary solutions of ethanol and methano
lhft_intern.bib::schuetz16

Highly Integrated 4–32-GHz Two-Port Vector Network Analyzers for Instrumentation and Biomedical Applications - Nehring, Johannes; Schütz, Martin; Dietz, Marco; Nasr, Ismail; Aufinger, Klaus; Weigel, Robert; Kissinger, Dietmar (IEEE Transactions on Microwave Theory and Techniques, 2017)
This paper addresses the miniaturization of microwave vector network analyzers (VNAs) and the future vision of the VNA on a chip. Therefore, a highly integrated two-port VNA with a multioctave bandwidth from 4 to 32 GHz is presented. The proposed system is based on a fully integrated radio-frequency frontend consisting of a two-port stimulus, a four-channel heterodyne receiver, and a wideband testset. The testset is comprised of on-chip multisection directional couplers. The chip is operated inside a hardware demonstrator using a 16-term calibration procedure. The measurement of arbitrary devices under test is in excellent agreement with commercial measurement equipment and showed a mean deviation from the reference measurement of 0.17 dB and 1.29° regarding the forward transmission of a coaxial 30-dB attenuator. The system and receiver dynamic ranges are 44-77 and 82-101 dB at a resolution bandwidth of 100 kHz over the full system bandwidth. The measurements are highly repeatable and are robust against drift over time. As a proof of concept, the developed integrated network analyzers are utilized in a biomedical sensing scenario with an external and an on-chip sensor. Both approaches showed good sensitivity regarding the mixture ratio of binary solutions of ethanol and methano
lhft_intern.bib::schuetz16

High Precision DOA Estimation of SSR Transponder Signals - Reck, C.; Berold, U.; Schmidt, Lorenz-Peter (ICWITS, 2010)
lhft_intern.bib::Reck10a

High-Precision Localization of Trapped Microparticles inside Hollow-Core Photonic Crystal Fibers using Coherent Optical Frequency Domain Reflectometry - Köppel, Max; Sharma, Abhinav; Renner, Esther; Xie, Shangran; Schmauß, Bernhard; Russell, P. St J. (2019 IEEE SENSORS, 2020)
We present a localization technique for an optically trapped microparticle inside hollow-core photonic crystal fibers which is the basis of a new generation of fiber optical sensors. A polystyrene particle of diameter 15 µm is optically trapped and moved inside the hollow-core fiber by optical forces while its position is tracked using coherent optical frequency domain reflectometry. We demonstrate that this technique can locate the particle position with a standard deviation of 10 µm. By applying a time-apertured Fourier transform, the dynamics of particle motion can be resolved with millisecond temporal resolutio

High-Precision Micromachining of Sapphire Towards Optical Waveguiding Structures using Femtosecond Lasers - Kefer, Stefan; Zettl, Julian; Schmauß, Bernhard; Esen, Cemal; Hellmann, Ralf (Proceedings of SPIE - The International Society for Optical Engineering, 2023)
While sapphire is one of the most durable materials, its properties entail that high-precision machining, especially in the sub-millimeter regime, is still challenging. This contribution demonstrates and discusses novel femtosecond laser-based micromachining approaches for the fabrication of rotational-symmetric sapphire workpieces, specifically the generation of optical fibers by means of laser lathe of sapphire rods and the practical realization of windmill fibers. In addition, volume refractive index modification in planar sapphire substrates is presented to induce photonic crystal waveguides. The micromachined structures are comprehensively examined with respect to geometric fidelity, surface roughness, refractive index modification, and potential optical waveguiding properties. All micromachining approaches are done by means of frequency-doubled or frequency-tripled femtosecond laser radiation. Different laser optical setups including laser scanning head, spatial beam profilers including a spatial light modulator and axial rotatory movement of the specimen are employed for micro structuring and in-depth refractive index modifications. In particular for laser lathe, a sophisticated scanning pattern, in combination with an incremental axial rotatory movement of the specimen, allows for the precise diameter reduction of sapphire rods with 250 µm diameter to fibers with outer diameters of 25 µm. By supporting the workpiece with a V-groove fixture, multi-mode fibers with lengths up to 20 cm can be processed with an average surface roughness of 250 nm. Additionally, an adapted ablation scanning sequence enables the first practical demonstration of sapphire windmill fibers. Furthermore, using a spatial light modulator allows for the adaption of the laser propagation properties as to enable volume refractive index modifications with free-form arrangement. Hexagonal patterns of refractive index modifications surrounding a pristine waveguide core are fabricated and single-mode waveguiding at 1550 nm is verified. Finally, the possibility of integrating Bragg gratings into this photonic waveguide type is demonstrated.
CRIS-Team Scopus Importer:2023-06-02
Keywords: Femtosecond Laser; Laser Lathe; Micromachining; Optical Waveguiding; Refractive Index Modification; Rod-to-Fiber; Sapphire

High Resolution Lensless Terahertz Imaging and Ranging - Damyanov, Dilyan; Friederich, Benedikt; Yahyapour, Milad; Vieweg, Nico; Deninger, Anselm; Kolpatzeck, Kevin; Liu, Xuan; Czylwik, Andreas; Schultze, Thorsten; Willms, Ingolf; Balzer, Jan C. (IEEE Access, 2019)
In this paper, we propose a fast terahertz time-domain imaging method using a radar migration algorithm. We demonstrate high-resolution imaging in reflection without any collimating or focusing optics in the terahertz beam. In the proposed method, the sample is illuminated with a divergent terahertz beam, and the receiver collects both specular and diffuse reflections. We further present calibration and post-processing methods that allow us to compensate for the inherently low signal-to-noise ratio of an unfocused terahertz beam. The feasibility of the novel imaging method is demonstrated with geometrically complex samples and a fast terahertz time-domain spectroscopy system based on electronically controlled optical sampling. We show that our concept is capable of generating images of the objects regardless of their size, shape, orientation and position relative to the transmitter and receiver antennas. Objects with edge lengths well below 400 μ m can be clearly detected. The method presented here thus lends itself to arbitrary scenarios and antenna configurations.
CRIS-Team WoS Importer:2019-12-06

High resolution permittivity reconstruction of one dimensional stratified dielectric media from broadband measurement data in the W-band - von Aschen, H.; Gumbmann, F.; Schmidt, Lorenz-Peter (Radar Conference (EuRAD), 2011 European, 2011)
For many security or Non Destructive Testing (NDT) applications it is desirable to detect and reconstruct dielectric stratified media to classify the investigated device under test (DUT). With rotational invariance techniques like the matrix pencil method (MPM) it is possible to improve the parameter estimation of a harmonic signal in contrast to the classical FFT based methods. By applying a time gating procedure prior to the MPM it is possible to reduce the influence of noise and multipath signals. Hence an improved parameter estimation is possible. Based on an optimized layer stripping algorithm it is possible to overestimate the number of layers in the stratified media and combine approximately similar layers.
lhft_intern.bib::aschen2011

High resolution position measurement of “flying particles” inside hollow-core photonic crystal fiber - Werzinger, Stefan; Bykov, Dmitry S.; Zeltner, Richard; Machnev, Andrey; Köppel, Max; Xie, Shangran; Schmauß, Bernhard; Russell, Philip St. John (IEEE Sensors Conference, 2017)
Optically trapped “flying particles” inside hollow core photonic crystal fiber (HC-PCF) can be used as multiparameter sensors of, for example, temperature, radiation levels or external electric fields. They represent a new type of optical fiber sensor, offering a spatial resolution that is only limited by the particle size, while being functionally reconfigurable. Here we demonstrate accurate measurement of the axial position of flying particles using incoherent optical frequency domain reflectometry in combination with model-based estimation processing. The approach allows to measure the particle position inside the HC-PCF with a precision of 140 μ

High sensitivity millimeter-wave detectors using fin-line technology - Meinel, H; Schmidt, Lorenz-Peter (IR and mm-Waves, 1980)
lhft_intern.bib::Schmidt80a

High-Speed, Large-Area POF Receivers for Fiber Characterization and Data Transmission >10-Gb/s Based on MSM-Photodetectors - Loquai, Sven; Winkler, Florian; Wabra, Stefan; Hartl, Engelbert; Schmauß, Bernhard; Ziemann, Olaf (Journal of Lightwave Technology, 2013)
The authors report on high-speed, very large-area, visible light photoreceivers suitable for large-core 1 mm polymer optical fibers (POF). The receivers are based on metal-semiconductor-metal photodetectors (MSM-PD) grown on gallium-arsenide (GaAs) substrate. Three active diameters of ø 1000 μ m, ø 700 μ m and ø 400 μ m were fabricated in order to meet the requirements of the following three specific POF applications. The first photoreceiver was designed to characterize the bandwidth of 1 mm POF. For that reason the receiver has an active diameter of ø 1000 μm to detect all modes at the end of the fiber. With this receiver the frequency response of 1 mm graded-index (GI-) POF was measured up to 12 GHz. The ø 1000 μm photoreceiver was designed for high-speed data transmission. Due to the large active area there is no need for an optical concentrator and the 1mmPOF can simply be butt-coupled to the receiver.With this receiver a novel real-time transmission of 10 Gb/s over up to 20 m GI-POF using simple non return to zero (NRZ) modulation is presented. For data rates beyond 10 Gb/s the ø 1000 μm photoreceiver with a 3-dB bandwidth of 11 GHz was designed. A record bit rate of 32 Gb/s was transmitted with this receiver over large-core 1 mm polymethylmethacrylate (PMMA) GI-POF. These achieved results are by far the best reported values for large-area visible light photoreceivers. © 1983-2012 IEE
UnivIS-Import:2015-03-09:Pub.2013.tech.IE.LEH.highsp
Keywords: Large-area; metal-semiconductor-metal; optical receivers; photodetectors; polymer optical fiber; visible light

Hochfrequenzanregung von Gas Lasern - Brand, Hans (Opto-Elektronik-Magazin, 1989)
lhft_intern.bib::thirty_years_LHFT_266

Hochfrequenztechnik im Terahertz-Bereich-Aufgaben, Lösungen, Herausforderungen - Brand, Hans (Archiv fuer Elektrotechnik, 1993)
Es wird begründet, weshalb elektromagnetische Wellen im Frequenzbereich von etwa 0,1 THz bis rund 10 THz aufgrund der physikalischen Situation der terrestrischen Atmosphäre bestimmte Aufgaben erfüllen können und weshalb andere in Bodennähe nicht. Zur Einführung in die nachfolgenden Beiträge werden die heute bekannten Systemlösungen summarisch skizziert. Die Diskussionen auf der Sindelfinger ITG-Sitzung am 28. 5. 1993 über Herausforderungen und Lösungsstrategien der Zukunft werden zusammenfassend wiedergegebe
lhft_intern.bib::thirty_years_LHFT_314

Hochfrequenztechnik in Beruf und Ausbildung des Elektroingenieurs - Brand, Hans; Schiek, B; Severin, H; Stegmeier, H; Thust, P; Unger, H (1988)
lhft_intern.bib::thirty_years_LHFT_249

Hochgenaue optische Abstandsmessung mittels kohärenter optischer Frequenzbereichsreflektometrie - Köppel, Max; Deckelmann, M; Werzinger, Stefan; Schmauß, Bernhard (Workshop der ITG-Fachgruppe 5.3.1 (Modellierung photonischer Komponenten und Systeme), 2018)

Hochstufige Modulation und Turbocodierung für GSM/ EDGE - Reck, Christoph (Friedrich-Alexander-Universität Erlangen-Nürnberg, 2007)

Hollow-core fiber Characterization with Correlation-Optical Time Domain Reflectometry - Azendorf, Florian; Schmauß, Bernhard; Shi, Bo; Fokoua, Eric Numkam; Slavik, Radan; Eiselt, Michael (2021 Optical Fiber Communications Conference and Exhibition, OFC 2021 - Proceedings, 2021)
Using a Correlation-OTDR, we characterized the temperature-induced group delay variations of two nested antiresonant nodeless hollow core fibers. The temperature sensitivity of both is substantially less than for SSMF with some dependency on coating type.
CRIS-Team Scopus Importer:2021-08-20

Holographic 3D Indoor Localization - Sippel, Erik (2022)
In the last twenty years, mobile communication systems have gone through a tremendous development, increasing the available consumer data rate by several orders of magnitude. Currently, the quickly emerging 5G and particularly the upcoming 6G technology renew the overall concept of communication networks by providing a universal standard, which is able to cover each part of the everyday life. In contrast, localization systems are mainly established within the global positioning system for outdoor navigation, while indoor localization systems are rare, particularly in the consumer sector. This is reasoned in the currently available implementations, which are either exact, but expensive using the broadband or ultra wide band technology or cheap, but very inexact via receive-signal-strength measurements. To deal with this problem, an alternative approach is studied in this thesis, which is based on the evaluation of spatially distributed phase measurements. Usually, spatially distributed phase measurements are recorded via antenna arrays. If the measurement process is incoherent, the phase-difference-of-arrival measurements are typically used to estimate the angle-of-arrival at each receiver, thereby assuming the impinging wave to be plane. Thereafter, the angular information of several receivers can be combined via multiangulation to calculate a beacon's position. This is done either individually for every measurement instances or recursively, for example using the extended Kalman filter. Though this broadly established method appears to be well suited at first glance, it restricts the achievable localization performance of indoor localization systems because of several reasons. First, the angle-of-arrival estimation depicts a non-linear mapping, whose result is only suitable for subsequent position estimation to a very limited extend because of noise shaping. Second, the impinging wave is assumed to be plane, which is only an approximation of the actually wave form, particularly indoors. Third, the localization accuracy mainly depends on the array's aperture size, which is strongly limited by the plane wave assumption. Hence, for highly accurate positioning an alternative approach is necessary, which does not rely on a plane wave assumption and does not perform any non-linear preprocessing, such as angle-of-arrival estimation. To avoid these limitations, holographic localization concepts estimate a beacon's position via brute-force searches, which quickly become computationally expensive in large areas, particularly for 3D positioning. To enable highly accurate, real-time 3D localization, the holographic extended Kalman filter approach is presented in this thesis, which directly evaluates phases or phase differences in a recursive extended Kalman filter based manner. Thus, the preprocessing is reduced to the phase extraction from complex valued signals, which implies minimal noise shaping, and the computation of phase differences, which is a linear mapping. Further, no assumptions about the received wave form are met and, therefore, the array apertures can be arbitrarily increased, strongly improving the achievable localization accuracy. Thereby, the reception of circular waves also reduces the influence of multipath propagation. In this thesis, the generally applicable holographic extended Kalman filter approach is implemented via the phase-difference holographic extended Kalman filter, which only evaluates phase differences and, hence, is applicable in many different applications, and via the quasi-coherent holographic extended Kalman filter, which involves the evaluation of absolute phases by assuming very stable frequency references, enabling extremely accurate tracking of changes of direction. To enable very accurate positioning via spatially distributed phase measurements, antenna arrays are necessary, which provide phase measurements on an equivalent level of accuracy. However, antenna arrays are impaired by channel phase mismatch, mutual coupling, and antenna position deviations. Usually, these are calibrated within anechoic chambers, which suppress the multipath propagation. Unfortunately, the antenna array impairments alter until the receivers are mounted into their final measurement environment. Therefore, an in-situ calibration method is proposed, which calibrates the receivers within the designated localization environment. Similar to the localization, the calibration measurements are performed within the arrays' near field to reduce the influence of the multipath propagation. Altogether, the proposed concepts enable indoor localization measurement with mm accuracy using a 24 GHz narrowband radar syste

Holographic Imaging Approach - Schildbach, C; Schmidt, Lorenz-Peter (Holographic Imaging Approach, 2017)
lhft_intern.bib::Schildbach2017

Holographic Localization of Passive UHF RFID Transponders - Miesen, Robert; Kirsch, Fabian; Vossiek, Martin (5th Annual IEEE International Conference on RFID (IEEE RFID 2011), 2011)
lhft_intern.bib::Miesen2011a

Homodyne Phase Sensitive Sub-millimetre Wave Transmission Measurements - Rehm, Guenther; Depser, J.; Schmidt, Lorenz-Peter (Proceedings of the 31st European Microwave Conference, 2001)
UnivIS-Import:2015-04-16:Pub.2001.tech.IE.LEH.homody

Human biological monitoring - A versatile tool in the aftermath of a CBRN incident - Mueller, Michael; Schmiechen, Katharina; Heselmann, Deike; Schmidt, Lukas; Göen, Thomas; Schmidt, Lorenz-Peter (Toxicology Letters, 2014)
Human biological monitoring (HBM) is a well established tool in occupational and environmental medicine. It allows to determine the internal dose of a chemical absorbed by an individual after acute or chronic exposure. Biological reference and threshold values may be used to evaluate the internal dose and estimate its health impact(s). HBM and its advantages have not been broadly recognized from a civil protection point of view in Germany, therefore we have designed a compendium to define state-of-the-art HBM sampling after a release of chemicals in a civil protection scenario. The compendium integrates the sampling of biological agents and the sampling of radio-nuclear target isotopes, to be analyzed by HBM, in a single sampling approach, thus limiting burden on the potentially exposed persons and facilitating comparison of their individual exposure to different CBRN agents. HBM analysis methods are evaluated and basic toxicity data (including biological reference and threshold values) are given for a list of 50 agents, previously identified as relevant in civil protection. For on scene commanders and healthcare professionals the compendium may help to generate HBM and biological-radio-nuclear (BRN) exposure data after a CBRN incident which can be used to improve risk communication.
EVALuna2:9717

Humidity-Induced Effects on Polymer Planar Bragg Gratings - Rosenberger, Manuel; Hessler, Steffen; Belle, Stefan; Schmauß, Bernhard; Hellmann, Ralf (IEEE Photonics Technology Letters, 2014)
The increasing dissemination of polymer materials in optics demands for a thorough understanding of their optical properties and their dependencies on ambient conditions. Here, we report on the influence of humidity on polymer planar Bragg gratings (PPBGs) in bulk polymethylmethacrylate (PMMA). We identify the contributions of both the humidity-induced variation of the grating period and the refractive index, which in turn results in a spectral shift of the Bragg wavelength. It is demonstrated that humidity saturated PPBGs show a change of the grating period as well as a rise of the refractive index resulting in a strong red shift of the reflection wavelength of about 4.24 nm. Furthermore, Bragg gratings are written into humidity saturated PMMA. After dehydration of the PMMA, the Bragg wavelength shows a permanent blue shift of 4.19 nm as compared with conventionally written Bragg gratings in dry PMM
lhft_intern.bib::Rosenberger2014c

Hybrid RFID System-based Pedestrian Localization: A Case Study - Wang, Haowei; Bauer, Georg; Kirsch, Fabian; Vossiek, Martin (10th Workshop on Positioning, Navigation and Communication 2013 (WPNC 2013), 2013)
Localization systems using RFID - especially passive RFID - are coming increasingly under the spotlight. Passive RFID has a relatively small sensing range compared to other radio-frequency-based localization techniques. Therefore in practice the deployed tags may not cover the whole scene of interest. Additionally, in the area of pedestrian localization, the unpredictable movement of pedestrians makes a complete RFID tag coverage extremely difficult. This paper introduces a hybrid RFID localization system used for indoor pedestrians to overcome the coverage shortfall associated with passive RFID tags. Two extra sources are used to assist the RFID system: local INS sensors and ZigBee nodes. A particle filter serves as a fusion framework. A test scenario was built with 220 RFID tags and 8 ZigBee nodes deployed in a museum. Different algorithms were evaluated in this deployment. The results show that the hybrid approach produces robust localization even with a low number of tags. © 2013 IEE
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.hybrid
Keywords: dead reckoning; fingerprinting; hybrid localization; particle filter; RFID

Hypersensitive H2 sensor based on polymer planar Bragg gratings coated with Pt-loaded WO3-SiO2 - Kefer, Stefan; Dai, Jixiang; Yang, Minghong; Schmauß, Bernhard; Hellmann, Ralf (Optics Letters, 2020)
This Letter demonstrates a novel, to the best of our knowledge, hydrogen sensor based on a polymer planar Bragg grating coated with Pt-loaded WO3-SiO2. The reflected Bragg signal shows a distinct peak splitting correlated to substrate anisotropies originating from the injection molding process. Especially at low H2 concentrations, both sensing peaks exhibit an outstanding response to the heat generated by the exothermic reaction between hydrogen molecules and coating. Thereby, a hydrogen volume ratio of 50 ppm leads to a Bragg wavelength shift of-37 pm, which yields an outstandingly low detection limit of only 5 ppm H2 in air. Thus, functionalized polymer planar Bragg gratings are eminently suitable for H2 leak detection applications.
CRIS-Team Scopus Importer:2020-07-24

ICs fuer den Mikrowellenbereich; GaAs-Bausteine fuer vielfältige Anwendungen - Feldle, H; Schmidt, Lorenz-Peter; Narozny, P; Coloquhoun, A; Werres, C; Splettstoesser, J (Elektronik, 1991)
lhft_intern.bib::Schmidt23

Identification of Ghost Moving Detections in Automotive Scenarios with Deep Learning - Martinez Garcia, Javier; Prophet, Robert; Fuentes, Michel Juan Carlos; Ebelt, Randolf; Vossiek, Martin; Weber, Ingo (IEEE MTT-S International Conference on Microwaves for Intelligent Mobility (ICMIM 2019), 2019)
We introduce a method to classify ghost moving detections in automotive radar sensors for advanced driver assistance systems. A fully connected network is used to distinguish between real and false moving detections in the occupancy gridmaps. By using this architecture, we combine the local Doppler information, along with the spatial context of the surrounding scenario to classify the moving detections. A proof of concept experiment shows promising results with data from a test drive in an urban scenari

Identifikation von Faserabschnitten basierend auf Rayleigh-Rueckstreumessungen mittels inkohärenter optischer Frequenzbereichsreflektometrie - Köppel, Max; Deckelmann, M; Schmauß, Bernhard (Workshop der ITG-Fachgruppe 5.3.1 (Modellierung photonischer Komponenten und Systeme), 2017)

IF-noise improvement of the GaAs Schottky diodes for THz-frequency mixer applications - Cojocari, O.; Biber, Stephan; Mottet, B.; Sydlo, C.; Hartnagel, H.; Schmidt, Lorenz-Peter (European Microwave Week 2003, 2004)
UnivIS-Import:2015-04-16:Pub.2004.tech.IE.LEH.ifnois

Illumination of humans in active millimeter-wave multistatic imaging - Ahmed, Sherif Sayed; Schmidt, Lorenz-Peter (European Conference on Antennas and Propagation (EUCAP), 2012)
The increasing demand on developing advanced imaging methods for the personnel screening applications has motivated many researchers to explore new techniques suitable to the emerging problem. Among the known methods, the active imaging using multistatic arrays in connection to digital-beamforming proofs efficient imaging with high image quality in terms of dynamic range and resolution. As any active imaging method, the illumination of the imaged object becomes an issue due to specular reflections. The human skin causes relatively strong specular reflections in the millimeter-wave range, and hence hinders the visibility of the body to some extend. Therefore, a consolidated understanding of the geometrical problem is essential for the optimization of the illumination issue. In this work, a simulation model is presented to address the problem precisely; and a measurement verification in the frequency range of 75 to 82 GHz is made to demonstrate the exactness of the proposed model. Additionally, an illumination analysis of a typical screening scenario of a human is presente
lhft_intern.bib::Ahmed2012

Illumination Properties of Multistatic Planar Arrays in Near-Field Imaging Applications - Ahmed, S. S.; Schiessl, A.; Schmidt, Lorenz-Peter (European Microwave Week, Paris, September, 2010)
The achievable illumination quality in microwave and millimeter-wave images using multistatic planar arrays is discussed. The geometrical relations between the array effective aperture and the illumination boundaries caused by the specular reflections are introduced. Afterwards, the variations in the processing gain due to diffuse and specular reflections are analyzed and verified experimentally.
lhft_intern.bib::Ahmed10

Image-Based Pedestrian Classification for Automotive Radar - Prophet, Robert; Hoffmann, Marcel; Ossowska, A; Malik, W; Sturm, C; Vossiek, Martin (15th European Radar Conference (EuRAD 2018), 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. In this paper, we present a novel pedestrian classification procedure, which uses image features from the range-Doppler-Matrix created by a 79 GHz chirp sequence radar. Experiments show single measurement success rates of 88% for a bandwidth of 1.6 GHz. Moreover, the robustness of the classification process is consolidated with a tracking algorithm. Implemented in vehicles, this can be a major contribution to protect vulnerable road user
lhft_intern.bib::Prophet18d

Imaging in scattering media using the phase of modulated light sources - Krämmer, P; Bartelt, H; Fischer, H; Schmauß, Bernhard (Proceedings of SPIE, 1995)
lhft_intern.bib::thirty_years_LHFT_352

Imaging of Moving Targets in Traffic Applications - Osterrieder, S; Gloeckler, R; Brand, Hans (1983)
lhft_intern.bib::thirty_years_LHFT_158

Imaging of plants using radiometry at 600 GHz - Rehm, G; Brand, Hans (IEEE, 1999)
lhft_intern.bib::thirty_years_LHFT_433

Imaging System for Non-Destructive Testing of Glass Fibre Reinforced Plastics - Nezadal, Martin; Schür, Jan; Schmidt, Lorenz-Peter (5th International Symposium on NDT in Aerospace, 2013)
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.imagin

Impact Damage Analysis of Composite Materials With a mm-Wave Synthetic Aperture Radar - Nezadal, Martin; Schür, Jan; Schmidt, Lorenz-Peter (Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on, 2013)
This paper presents investigations on impact damages on carbon and glass fibre reinforced plastics with a synthetic aperture radar in the frequency range of the W-Band (75 to 110 GHz) and J-Band (220 to 325 GHz). It was possible to detect the high energy impacts in the carbon fibre samples due to their phase delay in both bands. With the glass fibre samples it was also possible to detect changes in magnitude besides the phase delay. The three dimensional image reconstruction also revealed the damages beneath the surface. © 2013 IEEE.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.impact

Impact of ADC parameters on nonlinear compensation performance in 200 Gb/s polarization-multiplexed QAM transmission - Lin, Chien-Yu; Schmauß, Bernhard (IEEE Photonics Conference (IPC), 2013)
Nonlinear compensation based on digital backward propagation (DBP) is numerically implemented in 200 Gb/s polarization multiplexed (PM) PM-m-QAM un-compensated transmission. The impact of reduced ADC oversampling and quantization on DBP performance is analyzed.
lhft_intern.bib::Lin2013

Impact of channel baud-rate on logarithmic digital backward propagation in DP-QPSK system with uncompensated transmission links - Asif, Rameez; Lin, Chien-Yu; Schmauß, Bernhard (Optics Communications, 2011)
lhft_intern.bib::Asif2011a

Impact of Different Post-Processing Methods on a One-Receiver 2-Port Synthetic VNA Architecture - Schramm, Marcus; Hrobak, Michael; Schür, Jan; Schmidt, Lorenz-Peter; Konrad, M. (European Microwave Conference, Proceedings, 2011)
Production test of RF and electronic circuits is mainly driven by two restrictions, the initial investment in the equipment and the required measurement time, mostly describing the overall cost of test. This is one reason for the increased interest in synthetic instrumentation. The measurement of complex scattering parameters using synthetic instruments has been demonstrated. Improvement of the measurement accuracy and the speed while preserving a cost efficient solution is the focus of this contribution. Comparing the hardware demands using different calibration and post-processing steps gives an insight into a cost efficient design of a synthetic Vector Network Analyzer (sVNA).
lhft_intern.bib::Schramm11a

Impact of Surface Roughness on 3D printed SLS Horn Antennas - Lomakin, Konstantin; Pavlenko, Tatiana; Sippel, Mark; Gold, Gerald; Helmreich, Klaus; Ankenbrand, Markus; Urban, N; Franke, A (European Conference on Antennas and Propagation (EUCAP), 2018)

Implementation of 3D Automotive SAR Imaging - Noegel, Theresa; Reinecke, Marc; Schwenger, Lars; Heidbrink, Max; Hoffmann, Marcel; Vossiek, Martin (2024 21st European Radar Conference (EuRAD), 2024)
Autonomous vehicles demand a precise environmental understanding and are often reliant on radar technology for distance measurement and velocity evaluation. However, automotive radars suffer from poor angular resolution due to their limited aperture size. Synthetic Aperture Radar (SAR) mitigates this limitation by leveraging the vehicle’s movement to synthesize a larger aperture, which significantly enhances the angular resolution. While SAR has been utilized for 2D imaging in the automotive field, this work presents a novel approach to generate 3D SAR images by rotating a typical automotive radar sensor to obtain a real aperture in the elevation direction. By conventionally synthesizing the azimuth aperture through vehicle movement, a complete 3D SAR reconstruction of the environment becomes feasible. Real-world measurement results validate the theoretical expectations and demonstrate that additional height information can be provided. Based on these findings, we discuss the identified challenges, define measures to reduce the computational complexity, and derive a design proposal for a radar system suited for 3D automotive SAR application

Implementation of a Digital Shadow for Fiber Bragg Gratings - Renner, Esther; Härteis, Lisa-Sophie; Rittler, Andreas; Schmauß, Bernhard (Proceedings of the International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD, 2021)
We propose a synthesis model for fiber Bragg gratings (FBGs) to monitor temperature measurement errors due to aging behavior. This approach might be called a Digital Shadow since we are able to monitor all essential parameters of the grating to perform error prediction and consequently compensation. The model is tested during accelerated aging experiments, which furthermore reveal the shift of the center wavelength because of thermal decay.
CRIS-Team Scopus Importer:2021-10-22

Implementation of Real-Time Automotive SAR Imaging - Hoffmann, Marcel; Noegel, Theresa; Schüßler, Christian; Schwenger, Lars; Gulden, Peter; Fey, Dietmar; Vossiek, Martin (2023 20th European Radar Conference, 2023)
This paper presents measures to reduce the computation time of automotive synthetic aperture radar (SAR) imaging to achieve real-time capability. For this, the image formation, which is based on the Back-Projection algorithm, was thoroughly analyzed. Various optimizations were individually tested and analyzed on graphics processing units (GPU). Apart from the time reduction gained from these measures, the data size needed for processing was also drastically decreased. With a combination of all measures, a high-resolution SAR image of 30 m × 30 m that combines 8192 chirps can be reconstructed in less than 30 ms using a standard GPU. It is thus demonstrated that a real-time implementation of automotive SAR is possible.<br
Keywords: Power demand; Radar measurements; Graphics processing units; Radar imaging; Radar antennas; Real-time systems; Radar polarimetry; radar imaging; automotive radar; FMCW; SAR

Improved decision directed carrier phase estimation for nonlinearity mitigation in 16-QAM systems - Pakala, Lalitha; Schmauß, Bernhard (International Conference on Transparent Optical Networks (ICTON), 2014)
We propose and numerically investigate an improved decision directed (IDD) carrier phase estimation (CPE) to mitigate fiber nonlinearity in 16 quadrature amplitude modulation (QAM) coherent transmission systems. The proposed IDD-CPE algorithm is derived based on a two stage approach and compared with other CPE algorithms namely, the pre-decision directed (PDD) CPE and the decision directed (DD) phase locked loop (PLL). By exploiting the symbol position information in the I-Q plane and a euclidean distance measure, the proposed IDD-CPE algorithm outperforms the PDD-CPE and DD-PLL methods, exhibiting an optimal performance at signal launch power of 0 dBm and at optical signal to noise ratios (OSNRs) greater than 28dB, where no bit errors are detected.
lhft_intern.bib::Pakala2014b

Improved Threat Detection in Walk-Through Security Scanning Using an Optimized Polarimetric Target Decomposition Method - Root, Konstantin; Adametz, Julian; Gumbmann, Frank; Ullmann, Ingrid; Vossiek, Martin (IEEE Journal of Microwaves, 2022)
Reliable and convenient walk-through security scanning, which doesn't separate people or impede their movement, is an extremely challenging task. In this paper, a novel approach for a security check with an overhead observation and a polarimetric target decomposition is presented. The viewing angle of the scanner equals a side-looking airborne radar. However, it will be shown that the established polarimetric target decomposition methods of remote-sensing are not well suited for close-range radar imaging and need to be adapted due to the differences in the geometry of the imaging scenario. The usage of a multiple input and multiple output (MIMO) array and the shorter distance between array and target need a changed decomposition technique in order to distinguish between persons with or without worn threat objects. The differences between radar remote-sensing and close-range imaging scenarios are investigated. An optimized version of the Sato four-component polarimetric scattering decomposition is derived. The proposed close-range adjustment is applied to the model and investigated experimentally with a 4-to-12 GHz fully polarimetric MIMO imaging system. Polarimetric decomposition is carried out on defined test structures with known scattering mechanisms, as well as on mannequins and persons with different threat objects like guns or explosives. In test campaigns, promising results were achieved for a correct target decomposition in radar-based walk-through security scanning.<br

Improvement of accuracy for measurement of 100-km fibre latency with Correlation OTDR - Azendorf, Florian; Dochhan, Annika; Zou, Jim; Schmauß, Bernhard; Eiselt, Michael (IET Conference Publications, 2019)
We measured the latency of a 100 km fibre link using a Correlation OTDR. Improvements over previous results were achieved by increasing the probe signal rate to 10 Gbit/s, using dispersion compensation gratings, and coupling the receiver time base to an external PPS signal.
CRIS-Team Scopus Importer:2021-04-20
Keywords: Latency; Optical performance monitoring; Optical time-domain reflectometry

Improvement of NOLM-based phase-preserving amplitude limiters by fiber optimizations - Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Lasers and Electro-Optics (CLEO) and Quantum Electronics and Laser Science Conference (Qels), May, 2010)
lhft_intern.bib::Stephan10a

Incoherent Optical Frequency Domain Reflectometry for Distributed Raman and Bragg Fiber Temperature Sensors - Köppel, Max; Werzinger, Stefan; Engelbrecht, Rainer; Sutter, J; Bergdolt, Sven; Schmauß, Bernhard (18th International Conference on Sensors and Measurement Technology (SENSOR 2017), 2017)

Increasing Measurement Speed in mm-Wave Imaging Systems by Means of Frequency Multiplexing - Koeppel, Tobias; Methfessel, Sebastian Dirk; Schießl, Andreas; Schmidt, Lorenz-Peter (43th European Microwave Week, 2013)
Target movement during illumination causes reliability issues in imaging systems, particularly in applications where time efficiency is needed. A technique is proposed in order to reduce measurement time and as a consequence also motion blur effects. With the use of OFDM waveforms, a decrease in measurement time by a factor of 1.6 is achieved with minimal hardware costs. Measurement time for increasing numbers of carriers is predicted. A hardware realization is investigated with respect to hardware imperfections. Influence of intermodulation distortion and phase noise on dynamic range is discussed. Afterwards, imaging results are presented. © 2013 EMA.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.increa
Keywords: microwave imaging; multistatic radar; signal processing; sparse array

Independent Surveillance Broadcast – ADS-B Receivers with DOA Estimation - Reck, Christoph; Reuther, M.; Jasch, A.; Schmidt, Lorenz-Peter (ESAV'11, 2011)
On the one hand air traffic control (ATC) institutions consider to use ADS-B for its low cost and simplicity of ground station hardware. Aircraft positions transmitted via ADS-B are on the other hand in some cases error prone. In the proposed approach, direction of arrival (DOA) estimation is used to verify ADS-B airborne positions. The potential positioning error of ADS-B is thereby evaluated by comparing DOA estimates to DOA calculated from ADS-B references. To proof the accuracy of the applied DOA estimation sensor, an additional measurement campaign using a dedicated measurement aircraft has been conducted.
lhft_intern.bib::Reck2011b

In-Depth Characterization of a Dielectric Waveguide for mmW Transmission Line Applications - Distler, Felix; Schür, Jan; Vossiek, Martin (Proceedings of the 22nd IEEE Workshop on Signal and Power Integrity (SPI 2018), 2018)

Inductively Coupled Planar TX Coils: Analysis of B1+ Efficiency and SAR Performance - Schoepfer, Johanna; Huber, Klaus; Biber, Stephan; Vester, Markus; Martius, Siegfried; Vossiek, Martin (23^rd Annual Meeting & Exhibition of the International Society for Magnetic Resonance in Medicine, ISMRM 2015, 2015)
lhft_intern.bib::Schoepfer2015r

Influence of chemical polymer composition on integrated waveguide formation induced by excimer laser surface irradiation - Hessler, S.; Rosenberger, M.; Belle, S.; Schmauß, Bernhard; Hellmann, R. (Applied Surface Science, 2015)
We show that the chemical composition and the amount of residual monomers in polymethylmethacrylate significantly affect the evolution of optical waveguide formation induced by UV surface irradiation. We employ an interferometric approach in Mach-Zehnder configuration to determine the refractive index depth profile in different planar polymethylmethacrylate materials. Our results reveal a distinctive different surface and buried waveguide formation for materials having different monomer content. In particular, we find that for smaller residual monomer content buried waveguide formation is less pronounced, which is in turn preferential for a selective light guidance in planar polymer structures. Attenuation measurements confirm a difference in attenuation coefficient of 0.5 dB/cm.
lhft_intern.bib::hessler2015influence

Influence of gas dissociation and xenon addition on steady-state microwave-excited c02 laser discharges - Grudszus, S.; März, Martin (Journal of Physics D: Applied Physics, 1993)
The electron energy distribution in a microwave-excited mixture of He, N2, C02, Xe, CO and 02 was calculated by numerically solving the Boltzmann equation, using collision cross section data for 69 elastic and inelastic collision processes. At an excitation frequency of 2.45 GHz the energy distribution is quasi-stationary for gas pressures up to about 100 mbar. By balancing the most important processes of electron generation and loss, the reduced field E/N and the electron density nB in a seif-sustained steady-state discharge were calculated for various gas mixtures and excitation parameters. Curves are presented showing that with increasing C02 dissociation, the stationary value of E/N within the plasma rises, combined with drastically reduced rates for vibrational excitation of C02 (00*1) and N2. In contrast the admixture of xenon reduces the steady-state E/N value and thus the mean electron energy, leading to an increased electron density and excitation efficiency. These effects are in good agreement with experimental observations. © 1993 IOP Publishing Ltd.
Created from Fastlane, Scopus look-up

Influence of group-velocity dispersion on multilevel phase-preserving amplitude regeneration in a nonlinear amplifying loop mirror - Röthlingshöfer, Tobias; Toth, Daniel; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Transparent Optical Networks (ICTON), 2012)
Numerical simulations have shown a significant influence of group-velocity dispersion (GVD) of the highly nonlinear fiber on the transfer characteristics of a nonlinear amplifying loop mirror (NALM). The effect is especially strong for the anomalous dispersion regime where an interaction of GVD and self-phase modulation (SPM) leads to formation of high-order solitons. The irregularities of the resulting NALM transfer functions can be used for phase-preserving amplitude regeneration of several, irregular-spaced amplitude states for multi-level modulation formats. The regeneration performance was estimated for a 16QAM signal with three amplitude states where a reduction of amplitude noise without significant signal phase distortions has been observe
lhft_intern.bib::Roethlingshoefer2012ca

Influence of Group Velocity Dispersion on phase-preserving Amplitude Regeneration by a Nonlinear Amplifying Loop Mirror - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Lasers and Electro-Optics, 2008 and Conference on Quantum Electronics and Laser Science, pages 1-2, 4 - 8 May, 2008)
The influence of dispersion of the highly nonlinear fiber in the loop of a nonlinear amplifying loop mirror on its performance as a 2R regenerator for phase-encoded optical signals has been studied. © 2008 Optical Society of Americ
UnivIS-Import:2017-12-18:Pub.2008.tech.IE.LEH.influe

Influence of Rayleigh Backscattering on the Performance of NOLM-Based Phase-Preserving Amplitude Limiters - Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (OSA Optics and Photonics Congress, Advanced Photonics, BGPP Topical Meeting, Karlsruhe, 21.-24. Juni, 2010)
lhft_intern.bib::Stephan10

Influence of Rayleigh Backscattering on the Performance of NOLM-Based Phase-Preserving Amplitude Limiters - Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Conference on OFC / NFOEC, March, San Diego, 2010)
lhft_intern.bib::Stephan10b

Influence of systematic frequency-sweep non-linearity on object distance estimation in FMCW/FSCW radar systems - Pichler, Markus; Stelzer, Andreas; Gulden, Peter; Vossiek, Martin (33rd European Microwave Conference, EuMC, 2003)
The performance of frequency estimation procedures for sinusoidal signals in the presence of phase perturbations plays an important role in continuous-wave radar systems for distance measurement, as it directly determines the ranging accuracy. For the most widely used frequency estimator, the fast Fourier transformation, the influence of deterministic deviations of the transmit signal from the ideal curve in FMCW/FSCW radars is investigated, quantified and verified with measured radar data. © 2003 EUMA.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.influe

Influence of the Impulse Rebound on Optical Strain Sensors based on Step-Index Polymer Optical Fibers - Becker, Thomas; Werzinger, Stefan; Schmauß, Bernhard; Gehrke, Martin; Nkiwane, Emmanuel; Ziemann, O.; Engelbrecht, Rainer (POF Symposium at the Fiber Society Spring Conference, 2017)

Influence of the PCB Manufacturing Process on the Measurement Error of Planar Relative Permittivity Sensors Up To 100 GHz - Lau, Isabella; Hajian, Ali; Michler, Fabian; Gold, Gerald; Lurz, Fabian; Schmid, Ulrich; Helmreich, Klaus; Weigel, Robert; Kölpin, Alexander (IEEE Transactions on Microwave Theory and Techniques, 2019)
Accurate and precise knowledge of the relative permittivity of printed circuit board (PCB) materials is essential for the reliable design of high-frequency circuits. For simplicity reasons, planar, resonant permittivity sensors, which are directly integrated on the unknown PCB material, are widely used. However, the sensors are affected by the nonidealities of the copper-clad laminate and PCB manufacturing process, e.g., the difference in roughness between the top and bottom sides of each metal layer. This paper analyzes the influence of these nonidealities on the extracted relative permittivity values of different sensor geometries in microstrip and substrate integrated waveguide (SIW) technology up to 100 GHz. Microstrip resonators are very sensitive against the investigated nonidealities. Additional roughness measurements and more detailed simulation models cannot noticeably reduce the uncertainties. SIW cavity sensors are more robust, and simple modeling approaches lead to low uncertainties smaller than 0.05 for the whole frequency range from 10 to 100 GH
Keywords: Accuracy; manufacturingn process; materials nondestructive testing; microwave measurements; permittivity; printed circuit boards (PCBs); surface roughness; uncertainty.

Influence of the UV dosage on planar Bragg gratings in cyclo-olefin copolymer substrates - Rosenberger, M.; Schmauß, Bernhard; Hellmann, R. (Optical Materials Express, 2016)
We report on the influence of the applied UV dosage on the fabrication of planar Bragg gratings in cyclo-olefin copolymers. Integrated waveguides with inscribed gratings are fabricated simultaneously using a single writing step technique and characterized by measuring the reflected and transmitted spectra. In addition, the effect of length and width of both waveguide and Bragg grating on the reflectivity and attenuation are studied using the cut-back method. The results show that in this material class, integrated waveguides with an attenuation as low as 1.2 dB/cm and Bragg gratings with a reflectivity of up to 99% can be realized. Most strikingly, we demonstrate that Bragg gratings with a length of only 2.1 mm still exhibit a distinct Bragg reflection facilitating miniaturized Bragg grating applications. Moreover, we demonstrate that the refractive index sensitivity of the planar Bragg gratings strongly depends on the UV dosage, in turn facilitating to tailor grating properties according device requirements in sensing application
lhft_intern.bib::rosenberger2016influence

Influence of vibrations on the signals of automotive integrated radar sensors - Hau, Florian; Baumgärtner, Florian; Vossiek, Martin (2017 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility, ICMIM 2017, 2017)
For automotive radar sensors the challenge is to find an optimal packaging. In addition to the mounting and the installation behind bumpers and radoms, non-linear movements like vibrations have influences on the radar performance. Therefore, integration into the vehicle environment becomes more and more important. This paper presents a theoretical description about the effects of vibration on an automotive Chirp-Sequence-FMCW radar. The simulation results are compared to real radar measurements and show good agreement. The observed effects are analysed in detail and dicussed on signal level for different vibration regimes.
CRIS-Team Scopus Importer:2023-03-08

Inherent Resolution Limit Analysis for Millimeter-Wave Indirect Holographic Imaging - Adametz, Julian; Gumbmann, Frank; Schmidt, Lorenz-Peter (Frequenz, 2011)
In the classical indirect holographic setup, a wave emitted by the measurement object is superimposed with a reference wave at the aperture of the imaging system. The resulting interference pattern can be recorded with a simple intensity detection. However, the complex object field can be obtained from the plane wave spectrum (PWS) of the interference pattern. Dedicated methods can be used to calculate the field distribution at the object position, which is equivalent to the object properties and to an image of the object, respectively. This paper shows that the resolution of the created image is constricted due to the fact that the bandwidth of the extracted field is limited by the extraction process. A relation between the maximum possible bandwidth and the geometrical dimensions of the imager setup is deduced. Furthermore, a formula for the minimum achievable resolution is derived. Experimental results are presented to illustrate the issu
lhft_intern.bib::Adametz2014b

Innovative drahtlose Sensorkonzepte für das in-situ Monitoring von Aushärtevorgängen in Epoxidharzsystemen und Faserverbundbauteilen - Dorbath, Benedikt; Groh, Jannis; Schür, Jan; Vossiek, Martin (4. Symposium Materialtechnik, 2021)

Innovative optical components and their impact on future transmission systems - Schmauß, Bernhard; Striegler, Arne; Meißner, Markus (Invited talk, APOC, Wuhan, China, November, 2003)
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 system performance. In terms of signal distortion besides advanced link design strategies optical regenerators are of high interest for signal conditioning along a fiber link. Our paper reviews signal regeneration techniques focusing on fiber nonlinearity based setups both in interferometric and non interferometric architecture. We analyze the impact of regenerator design parameters as fiber nonlinear parameters, regenerator input power and characteristics of filters on signal improvement and demonstrate e.g. the increase of system reach. In order to address the upcoming techniques of advanced modulation formats we introduce a fiber based regenerator scheme that shows attractive potential especially for phase modulated signals. Combining these new optical formats with regenerative methods is attractive for high performance systems. For the differential phase shift keying (DPSK) modulation format we investigate the potential of a cross phase modulation based type of regenerator in more detail. The availability of suitable regenerator components, especially highly nonlinear fibers is one of the challenges. Especially the new fiber types known as photonic crystal fibers can act as bases for new structures and thus will open the door for ultra high performance optical transmission systems.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.innova
Keywords: Modulation Format; Optical Transmission; Regeneration

In-Situ Calibration of Antenna Arrays within Wireless Locating Systems - Sippel, Erik; Lipka, Melanie; Geiß, Johanna; Hehn, Markus; Vossiek, Martin (IEEE Transactions on Antennas and Propagation, 2020)
Antenna arrays are frequently used for localization of active communication transmitters or passively reflecting radar targets by evaluating signal phases at spatially distributed antennas. Unfortunately, the localization performance is degraded because of mutual coupling, unknown time delays, and imprecisely known antenna positions, especially if large arrays with spatially distributed antennas are used. Furthermore, these errors are altered until the array is steadily installed at its destination, which occurs because of position misalignment and cable phase instability. Hence, an in-situ array calibration is necessary to perform faultless phase measurements. For this purpose, this article proposes a novel calibration procedure for antenna arrays, correcting both the mutual coupling and positioning errors using an incoherently transmitting beacon. Because the in-situ calibration will be affected by multipath, measurements at random reference positions within the array’s near field are used for calibration. In addition, the algorithm copes with randomly varying path losses because of unknown antenna polarizations and patterns. Calibration measurements are performed, providing physically reasonable results without using an anechoic environment. Furthermore, the calibration results are validated via indoor localization using three antenna arrays that were calibrated with the proposed algorith
Keywords: Radar; indoor navigation; localization; calibration; antenna array; mutual coupling

Instantaneous Ego-Motion Estimation Using a Coherent Radar Network - Hoffmann, Marcel; Krabbe, Lena; Schüßler, Christian; Gulden, Peter; Vossiek, Martin (2022 19th European Radar Conference (EuRAD), 2022)
This paper presents an approach to estimate the ego-motion of a vehicle equipped with a network of two or more coherently working bistatic or multistatic MIMO radars. The multi-perspective view of this setup allows for an immediate determination of the radar targets' relative velocity vector. The ego-motion is then derived from the inverted vectorial velocity of all static targets that can be obtained by clustering the velocity vectors. For this, it can be assumed that the majority of the detected targets are static, thus generating the largest cluster. The novel approach was tested with a setup consisting of two 77 GHz front-looking, long-range radars that only exhibit a narrow field of view with a small azimuth variation. The functionality of the proposed algorithm was evaluated and confirmed in a highway test driv
Keywords: motion estimation; Doppler radar; wireless sensor networks; automotive applications

Instantaneous Ghost Detection Identification in Automotive Scenarios - Prophet, Robert; Martinez Garcia, Javier; Fuentes, Michel Juan Carlos; Ebelt, Randolf; Vossiek, Martin (Radar Conference 2019, Boston (MA), USA, April 2019, 2019)
This paper addresses one of the most serious drawbacks of automotive radar sensors: The frequent occurrence of ghost detections. As such detections may cause undesired behavior, they need to be partially or completely eliminated. We present an algorithm, which uses a machine-learning-based classifier to distinguish between real and ghost detections. In contrast to other papers, this approach addresses all causes of ghost detections and not only simple multipath scenarios. Real world experiments – also in challenging situations – show success rates of 91

Integrated Front-End Approaches for Wireless 100 Gb/s and Beyond: Enabling Efficient Ultra-High Speed Wireless Communication Systems - Carlowitz, Christian; Dietz, Marco (IEEE Microwave Magazine, 2023)
Wireless communication faces ever-growing demand for higher data rates, which has driven the need for modem implementations that are capable of providing single-link data rates on the order of 100 Gb/s and beyond for extremely fast data transmission. In recent years, the 60-GHz band has been employed to significantly increase wireless local area network data rates in IEEE’s 802.11ad standard targeting multigigabit modems. Its extension 802.11ay was finalized in 2021, targeting data rates toward 100 Gb/s in the same bands by increasing spectral efficiency and combining up to four channels with more than 8-GHz bandwidth in total [1] . This approach has the advantage of existing unlicensed regulatory allocations. Nevertheless, options for higher bandwidth have increasingly been investigated, also driven by the publication of the IEEE 802.15.3d [2] physical layer standard for a frequency range between 252 and 325 GHz, which resides in an atmospheric window that enables reasonable long-range communication links on the order of a few kilometers. In this frequency range, a substantially higher bandwidth is achievable. Specific regulatory allocations are still missing; nevertheless, the conditions to use this frequency range have already been discussed and described during the 2019 World Radiocommunication Conference [3] . Although the first demonstrations of 100-Gb/s modems in this frequency range were at least partially based on photonic technologies [4] , integrated front ends in different semiconductor technologies have been demonstrated [5] and are discussed in the present article in more detail together with the major remaining challenges for practical applications.<br
Keywords: Wireless communication; Wireless LAN; Spectral efficiency; Bandwidth; Modems; Transceivers; Resource management

Integrated Self-Contained Trajectory Estimation and Multistatic SAR Imaging in a Non-Static Uncoupled Bistatic Radar Network - Fenske, Patrick; Kögel, Tobias; Ghasemi, Roghayeh; Gunders-Hunt, Danielle; Vossiek, Martin (IEEE Journal of Microwaves, 2025)
Radar imaging performance can be significantly improved by creating synthetic apertures along a radar sensor's trajectory compared to standard MIMO imaging radars. Additionally, observing the scenery from both monostatic and bistatic perspectives with large bistatic angles can further increase the information content of radar images, as different parts of complex targets can exhibit different scattering mechanisms. Both technologies, synthetic aperture radar and coherent multistatic radar networks, come with demanding system requirements regarding the localization and synchronization of the involved radars, which are addressed by the proposed approach. The unique aspect of our novel bi-/multistatic radar approach is that no auxiliary sensor technology is needed to determine the trajectory. The same radar signals are jointly used at the same time for trajectory determination, clock synchronization, and bistatic SAR imaging. The integrated self-contained trajectory estimation is based on a particle filter algorithm that processes the line-of-sight radar signals of the bistatic radar pairs, which are exchanged in a double-sided two-way ranging manner. This approach opens up new applications of bi-/multistatic radar for autonomous air and ground vehicles. However, the requirement of a line-of-sight connection between the radar pairs imposes a constraint on possible bistatic constellations and trajectories. Therefore, it is shown that suitable compromises regarding the geometry, localization accuracy, and resolution of SAR imaging must also be taken into account. We demonstrate the capabilities of this approach by generating monostatic and bistatic SAR images with 77 GHz SIMO FMCW radar sensors from indoor and outdoor measurement scenarios with synthetically generated apertures estimated by the integrated self-contained localization algorith
Keywords: Bistatic radar; cooperative radar networks; FMCW; localization; multiperspective imaging; SAR; synchronization

Integration and Performance Aspects of Automotive Radar at Millimeterwave and Sub-Millimeterwave Frequencies - Köhler, Aaron; Schür, Jan; Vossiek, Martin; Schmidt, Lorenz-Peter (IEEE MTT-S International Microwave Symposium 2015 (IMS 2015), 2015)
lhft_intern.bib::Koehler2015

Integration Concepts for Submillimeterwave Frequency Multipliers - Shaalan, M; Grueb, A; Simon, A; Krozer, V; Hartnagel, H; Steup, D; Brand, Hans (1995)
lhft_intern.bib::thirty_years_LHFT_365

Integration radarbasierter Fahrerassistenzsysteme in Kunststoffkarosserieteile - Fuchs, Michael; Drummer, Dietmar; Kilian, Andreas; Schmidt, Lorenz-Peter (Automotive meets Electronics, 2010)
UnivIS-Import:2015-04-16:Pub.2010.tech.IE.LEH.integr

Intelligenter Luftultraschall-Präsenz- und Lagedetektor für Förderanlagen. Intelligent airborne ultrasonic presence and position detector for conveyor installations. - Vossiek, Martin; Eccardt, P.-C.; Lechner, T.; Kroemer, N.; Magori, V. (ITG-Fachberichte, 1994)
UnivIS-Import:2015-04-16:Pub.1994.tech.IE.LEH.intell

Intelligente Sensorsignalverarbeitung durch Kombination von Fuzzy-Logik und klassischer Signalvorverarbeitung am Beispiel eines Luftultraschallsystems zur Platinenbestückungskontrolle - Vossiek, Martin; Eccardt, P.-C.; Magori, V.; Ermert, Helmut (Konferenz-Einzelbericht: Technische Anwendungen von Fuzzy-Systemen, 1992)
UnivIS-Import:2017-12-18:Pub.1992.tech.IE.LEH.intell

Intelligent Reflecting Surface Assisted Free-Space Optical Communications - Jamali, Vahid; Ajam, Hedieh; Najafi, Marzieh; Schmauß, Bernhard; Schober, Robert; Poor, H. Vincent (IEEE Communications Magazine, 2021)
Free-space optical (FSO) systems are able to offer the high data-rate, secure, and cost-efficient communication links required for applications such as wireless front- and backhauling for 5G and 6G communication networks. Despite the substantial advancement of FSO systems over the past decades, the requirement of a line-of-sight connection between transmitter and receiver remains a key limiting factor for their deployment. In this article, we discuss the potential role of intelligent reflecting surfaces (IRSs) as a solution to relax this requirement. We present an overview of existing optical IRS technologies; compare optical IRSs with radio frequency IRSs and optical relays; and identify various open problems for future research on IRS-assisted FSO communications.
CRIS-Team WoS Importer:2021-12-10

Intelligent Reflecting Surfaces for Free Space Optical Communication Systems - Najafi, Marzieh; Schmauß, Bernhard; Schober, Robert (IEEE Transactions on Communications, 2021)
In this paper, we investigate the use of intelligent reflecting surfaces (IRSs) to relax the line-of-sight requirement of free space optical (FSO) systems. Considering a Gaussian laser beam, we first design a phase-shift distribution across the IRS that enables the reflection of the incident beam in any desired direction, i.e., realizing the generalized law of reflection. Moreover, for the designed phase-shift profile, we show that there exists an equivalent mirror-assisted FSO system that generates a reflected electric field on a mirror that is identical to that on the IRS in the original system. However, the location of the laser source and the properties of the emitted Gaussian laser beam are different in the original and the equivalent systems. This equivalence allows us to study the mirror-assisted system, employing the image method from geometric optics, instead of directly analyzing the original IRS-assisted system. Based on this analysis, we model the geometric and misalignment losses (GML) and characterize the impact of the physical parameters of the IRS, such as its size, position, and orientation, on the end-to-end FSO channel. Moreover, we develop a statistical model for the GML which accounts for the random movements of IRS, transmitter (Tx), and receiver (Rx) due to building sway. Furthermore, we analyze the outage probability of an IRS-assisted FSO link based on the derived channel model. Our simulation results validate the accuracy of the developed channel model and offer various insights for system design. For instance, both our simulations and theoretical analysis reveal that even if the variances of the fluctuations of the Tx, IRS, and Rx positions caused by building sway are identical, their impact on the end-to-end channel is not necessarily the same and depends on the relative positioning of these three nodes.
CRIS-Team Scopus Importer:2021-06-11
Keywords: anomalous reflection; Buildings; Channel models; free space optical systems; geometric and misalignment losses; Intelligent reflecting surfaces; Laser beams; Lenses; line-of-sight link; Mirrors; Optical surface waves; Optical transmitters; pointing error

Intensity referencing in an extrinsic optical fiber temperature sensor - Apelsmeier, A.; Gleixner, R.; Shamonin, B.; Schmauß, Bernhard (Procedia Engineering, 2010)
Optical fiber sensors based on intensity measurement require some form of intensity referencing to avoid errors arising from parasitic losses. Known techniques of referencing such as balanced bridge, divided beam systems or two-wavelength referencing are not suitable for low-cost applications since they use relatively complicated optical components such as multiple LED sources, couplers, filters etc. In this work a novel method of referencing in an extrinsic optical fiber sensor system utilizing temperature dependence of absorption edge in a semiconductor crystal is described. The sensor system comprises a single LED source and no optical fiber junctions. The emission spectrum of an LED depends on its temperature. The reference is provided by controlling the temperature of an LED source and transmission measurements with different emission spectra. The entire process is controlled by a microprocessor unit. Performance of a sensor system is investigated and it is shown that the losses in connectors may be compensated for.
UnivIS-Import:2015-03-09:Pub.2011.tech.IE.LEH.intens
Keywords: Extrinsic optical fiber sensor; Intensity referencing; Temperature measurement; Absorption edge; Semiconductor; Hot-spot measurement

Interconnects and Chip Modules for Broadband Digital Systems with Bitrates up to 80 GB/S - Nisznansky, Martin; Ziegler, Christof; Martius, Siegfried; Schmidt, Lorenz-Peter (13th Conference on Microwave Techniques, Prague, September 26-28, 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.interc

Intercore–gain–crosstalk in multicore fiber amplifiers for telecommunication applications - Beck, Benedikt; Yildiz, Benjamin; Rapp, Lutz; Schmauß, Bernhard; Walbaum, Till (Photonic Networks; 24th ITG-Symposium, 2023)
Spatial division multiplexing is the only currently known technique to cope with the forecasted demand for capacity in the long term. Of particular interest is its implementation as multicore fiber system, which offers further capacity increase while simultaneously reducing cost and energy consumption per throughput. Essential components in such a transmission system are cladding pumped multicore amplifiers, which allow for signal amplification in multiple cores via a single uncooled multimode pump. However, above mentioned advantageous features could come with the detriment of a coupling of the pump powers available for amplification in the different cores. The resulting gain crosstalk is investigated by means of simulations for various signal power distribution schemes across the cores. In particular, gain variations in all cores are demonstrated to be negligible for signal power changes in other core
Keywords: Multicore; EDFA; Glaserfaser; Optische Übertragungstechnik

Interrogation of 2000 Draw Tower Gratings for Quasi Distributed Sensing with Coherent-Correlation-OTDR - Azendorf, Florian; Voigtländer, Christian; Lindner, Eric; Schmauß, Bernhard; Eiselt, Michael (Optics InfoBase Conference Papers, 2022)
Utilizing a Coherent-Correlation-OTDR, 2000 draw tower gratings in 100 meter fiber with a spatial resolution of 50 mm were successfully interrogated. Spooling of the fiber results in variations of the FBG reflection spectra.
CRIS-Team Scopus Importer:2022-10-21

Interrogation von FBG Arrays in komplexen Sensornetzwerken mittels IOFDR - Härteis, Lisa-Sophie; Schmauß, Bernhard (ITG-Workshop KT31 (Modellierung und Simulation photonischer Komponenten und Systeme), 2020)

Inverse filter technique for high-precision ultrasonic pulsed wave range Doppler sensors - Ruser, H.; Vossiek, Martin; von Jena, A.; Magori, V. (IEEE International Conference on Acoustics, Speech, and Signal Processing, IEEE ASSP Conference, 1997)
Ultrasonic pulsed wave range Doppler sensors provide application in various fields, e.g. intruder alarm systems or autonomous vehicle steering. The time-frequency methods commonly used in these sensors, however, inhere the problem that, due to the transducer's non constant and direction-dependent transfer functions, the Doppler frequency cannot be determined with high accuracy needed for such applications. The easiest way to improve the Doppler resolution is to reduce the signal bandwidth, but only at the expense of worse range resolution. In this paper a direction-dependent inverse filter technique is presented, which compensates erroneous effects of the transfer function in the time-frequency analysis. An ultrasonic intruder alarm system determining location and velocity of persons in rooms serves as an example that the novel approach gives evidently better performance than conventional methods, resulting in both high velocity and range resolution.
UnivIS-Import:2015-04-16:Pub.1997.tech.IE.LEH.invers

Inverse Methods in Electromagnetic Imaging - Boerner, W; Brand, Hans; Cram, L; Gjessing, D; Jordan, A; Keydel, W; Schwierz, G; Vogel, M (Springer Netherlands, 1985)
lhft_intern.bib::thirty_years_LHFT_201

Inverse Rendering of Near-Field mmWave MIMO Radar for Material Reconstruction - Hofmann, Nikolai; Wirth, Vanessa; Bräunig, Johanna; Ullmann, Ingrid; Vossiek, Martin; Weyrich, Tim; Stamminger, Marc (IEEE Journal of Microwaves, 2025)
Near-field multiple-input multiple-output (MIMO) radar systems allow for high-resolution spatial imaging by leveraging multiple antennas to transmit and receive signals across multiple perspectives. This capability is particularly advantageous in challenging environments, where optical imaging techniques struggle. We present a novel approach to inverse rendering for near-field MIMO radar systems, aimed at reconstructing material properties such as surface roughness, dielectric constants, and conductivity from radar and ground-truth mesh data, for example obtained from multi-view stereo. Drawing inspiration from physically based rendering techniques in computer graphics, we formalize an advanced inverse rendering algorithm that integrates electromagnetic wave propagation models directly into the optimization process. To avoid bias from conventional radar image reconstruction algorithms in the optimization process, we directly derive gradients from raw radar outputs, resulting in more accurate material characterization. We validate our approach through extensive experiments on both synthetic and real radar datasets, demonstrating its effectiveness in a multitude of scenario
Keywords: Backpropagation; MIMO radar; radar simulation; ray tracing; scattering parameters

Inverse SAR Approach for Localization of Moving RFID Tags - Parr, Andreas; Miesen, Robert; Vossiek, Martin (7th Annual IEEE International Conference on RFID (IEEE RFID 2013), 2013)
This paper presents an inverse synthetic aperture radar approach for localizing standard UHF RFID transponders. The proposed method is a powerful option to estimate the positions of tags that pass RFID gates or read points. A priori information about the relative transponder trajectory, such as the speed of a conveyor belt or a trajectory created by a robotic arm or rotary table, is used to generate an inverse synthetic aperture. Sampled phase data from RFID signals which are backscattered to single or multiple antennas combined with the information on the relative RFID tag trajectory are used to reconstruct the tag's absolute trajectory. The paper describes basic properties of synthetic apertures in RFID systems and methods of evaluating beam patterns based on array beam steering theory. Simulations of a conveyor belt scenario and test data acquired from an industrial rotary table transporting tagged objects are described. The experimental results prove that our novel method enables robust localization of moving RFID tags even in a severe multipath environment. © 2013 IEEE.
UnivIS-Import:2015-04-16:Pub.2013.tech.IE.LEH.invers
Keywords: holography; phased arrays; position measurement; radiofrequency identification; RFID tags; synthetic aperture radar

Inverse Synthetic Aperture Secondary Radar Concept for Precise Wireless Positioning - Vossiek, Martin; Urban, Alexander; Max, Stephan; Gulden, Peter (IEEE Transactions on Microwave Theory and Techniques, 2007)
In this paper, the novel inverse synthetic aperture secondary radar wireless positioning technique is introduced. The proposed concept allows for a precise spatial localization of a backscatter transponder even in dense multipath environments. A novel secondary radar signal evaluation concept compensates for the unknown modulation phase of the returned signal and thus leads to radar signals comparable to common primary radar. With use of this concept, inverse synthetic aperture radar algorithms can be applied to the signals of backscatter transponder systems. In simulations and first experiments, we used a broadband holographic reconstruction principle to realize the inverse synthetic aperture approach. The movement of the transponder along a short arbitrary aperture path is determined with assisting relative sensors (dead reckoning or inertia sensors). A set of signals measured along the aperture is adaptively focused to the transponder position. By this focusing technique, multipath reflections can be suppressed impressively and a precise indoor positioning becomes feasible. With our technique, completely new and powerful options for integrated navigation and sensor fusion in RF identification systems and wireless local positioning systems are now possible. © 2007 IEEE.
UnivIS-Import:2015-03-09:Pub.2007.tech.IE.LEH.invers
Keywords: Position measurement; Radio navigation; Secondary radar; Synthetic aperture radar (SAR); Transponders

Investigating Laser Direct Structuring and Aerosol-Jet for Additively Manufactured Helix Antennas - Ankenbrand, Markus; Panusch, David; Piechulek, Niklas; Gold, Gerald; Helmreich, Klaus; Franke, Jörg (2024 International Conference on Electronics Packaging, ICEP 2024, 2024)
This paper investigates the manufacturing of helix antennas using additive technologies, highlighting the influences of substrate surface quality and manufacturing processes on antenna characteristics. The focus lies on Fused Filament Fabrication and Digital Light Synthesis for the substrate generation, and Aerosol-Jet and Laser Direct Structuring (LDS) for functional structuring. The tested materials are PEEK, epoxy and polycarbonate for the substrate and silver and copper for the traces. Challenges encountered during manufacturing include spreading of the ink in Aerosol-Jet printing, and short circuits caused by smoke residues in LDS. The radiation patterns of the additively manufactured antennas are compared with simulated responses and a subtractively manufactured reference, revealing a small but measurable impact of geometric deviations and surface roughness on performance.
CRIS-Team Scopus Importer:2024-06-21
Keywords: Additive Manufacturing; Helix Antenna; Laser Direct Structuring; Printed Electronics

Investigating plasmonic gap modes coupled to nanoantennas - Wen, J.; Kriesch, Arian; Ploss, Daniel; Banzer, Peter; Schmauß, Bernhard; Peschel, Ulf (Lasers and Electro-Optics Europe (CLEO EUROPE/EQEC), 2011 Conference on and 12th European Quantum Electronics Conference, 2011)
lhft_intern.bib::Wen2011

Investigating Spiral Antennas for Interstitial Microwave Hyperthermia - Erb, J; Ngo, C; Schaller, G; Engelbrecht, Rainer (1999)
lhft_intern.bib::thirty_years_LHFT_436

Investigation of a Simple and Versatile Concept for OFDM Radar Target Simulator Enhancement - Birkenhauer, Christoph; Körner, Georg; Stief, Patrick; Hamberger, Gerhard; Beer, Matthias; Carlowitz, Christian; Vossiek, Martin (2024 IEEE Radio and Wireless Week, RWW 2024 - 2024 IEEE Topical Conference on Wireless Sensors and Sensor Networks, WiSNeT 2024, 2024)
This paper investigates the use of a modulation technique for radar target simulators (RTSs) that significantly improves their performance regarding dynamic range and multi angle capabilities. The technique, which has been examined for frequency-modulated continuous wave (FMCW) previously, is also applicable to orthogonal frequency-division multiplexing (OFDM) radar RTSs. It allows increases in the dynamic range and a finer gain adjustment by adjusting the mean value of the modulation. In addition, a low-cost multi-angle RTS can be realized using this approach by combining established RTS techniques with an additional suitably designed on-off modulation. While the advantages of this approach have already been demonstrated for FMCW radar sensors, this work focuses on the applicability of the technique to OFDM radars. A practical implementation of the proposed RTS enhancement technique is experimentally investigated for an experimental OFDM radar system. Our results show that the proposed method offers great practical advantages for improving RTSs even for multi-carrier radar signals, especially when cost is a major concern.
CRIS-Team Scopus Importer:2024-03-15
Keywords: automotive radar; OFDM radar; radar target simulation

Investigation of the effects of energy density in Laser Sintering of polypropylene on morphological and dielectric properties for high-frequency antennas - Romeis, Manuel; Ehrngruber, Michael; Drummer, Dietmar (Procedia CIRP, 2024)
Advancements in the Internet of Things demand more capable antenna systems, which benefit from the complex geometries enabled by additive manufacturing. Novel approaches, such as external metallization of polymers, enable the design of these geometries but require the processing of low dielectric-loss polymers in additive manufacturing. Arising from prevailing limitations on additively manufactured low-loss components, this study investigates the effect of energy density on polypropylene's dielectric properties in powder bed fusion processes. Variations in laser power significantly influenced material density and mechanical characteristics. Both insufficient and excessive energy densities resulted in lower quality parts due to issues like fused particles or inadequate melting. Optimal dimensional accuracy and surface quality were achieved with energy levels slightly below those for peak density. While dielectric loss remained mostly stable, relative permittivity decreased at very low densities, where partial melting occurred. Relying on derived optimized parameters, the functionality of passive high-frequency components was demonstrated.
CRIS-Team Scopus Importer:2024-09-27
Keywords: high-frequency antenna; Laser Sintering (SLS); polypropylene

Investigation of the Electromagnetic Wave-Tissue Interaction of a 75–110 GHz Reflective Resonator Probe for Tissue Classification - Hecht, Damaris; Pfahler, Tim; Vossiek, Martin (2024 54th European Microwave Conference (EuMC), 2024)
In this work, the interaction of a 75–110 GHz reflective resonator probe with biological tissue is investigated for both tactile and non-contact measurements. A proof of concept of the principle and an approach for highly accurate tissue classification were provided in previous work – for tactile in vivo measurements. However, for some classification tasks, such as the assessment of burn wounds, non-contact measurements are preferable. The next step towards a non-contact application is therefore to investigate how distances between the probe tip and the tissue surface affect the field distribution in the tissue and the reflectance spectra measured by the probe, as the spectra form the basis for subsequent tissue classification. In this work, the setup of the probe was modeled for different distances to the skin surface, from 0–1 mm. The resulting electric field distribution in the tissue and the reflection coefficient spectra are presented and discussed. Based on the simulation results, the existing classification concept is suitable for non-contact measurements with small distances of 0.1 mm or less.
Created from Fastlane, Scopus look-up
Keywords: biomedical sensing; burn wound assessment; millimeter-wave near-field spectroscopy; resonant sensor; tissue classification; tissue modeling; wave-tissue interaction

Investigation of the hot embossing technology for low-cost antennas printed on polymer substrates - Kilian, Andreas; Weinzierl, Jochen; Schmidt, Lorenz-Peter (38th European Microwave Conference, EuMC 2008, 2008)
In this contribution a novel metallization technique for the realization of millimeter-wave microstrip patch antennas is presented. This technology called hot embossing is a fast and economic process originating from the production of threedimensional molded interconnect devices (3D-MID). Conductive structures are coated onto plastic parts or plastic foils using a heated stamp. To the best knowledge of the authors, this approach has not yet been employed and therefore will be investigated for the fabrication of low-cost printed antennas at millimeter-wave frequencies. The focus of this contribution is on the evaluation of process parameters and interactions with substrate and copper foil characteristics as well as the fabrication and measurement of single microstrip patch antennas designed for the 24 GHz ISM- band. Far-reaching potentials lie in the utilization of the threedimensional manufacturing technology for the construction of conformal integrated antennas. © 2008 EuMA.

Investment Casting of Microwave Components for E-Band - Panusch, David; Birkenhauer, Christoph; Gold, Gerald (European Microwave Week 2024, 2024)
The investment casting process was newly proposed for the production of microwave components, combining the advantages of additive manufacturing’s spatial freedom with an all-metal structure that was previously unavailable for the E-Band. This paper focuses on the effects of the manufacturing process of these components on casting quality and resulting electrical properties, which can be up to 2 dB better with adopting suitable design for manufacturing methods. The effective conductivity of different casting specific alloys is analyzed utilizing a resonator measurement, whereby an improvement of 20% from fine silver to an aluminium alloy could be determined. The results are compared to a conventional milled waveguide as a reference. Additionally, the waveguides slotted sidewalls are examined in a crosstalk stud
Keywords: 3D-printing; Additive Manufacturing; Conductivity Measurement; Slotted Waveguide; E-Band; lost wax casting; surface roughness; effective conductivity

Invisible Sensing: Radar-based Biomonitoring - Eskofier, Björn; Vossiek, Martin (IEEE Open Journal of Engineering in Medicine and Biology, 2024)
CRIS-Team Scopus Importer:2024-06-14
Keywords: Biomedical monitoring; Machine learning; Medical services; Monitoring; Older adults; Radar; Sensors

In-vitro Evaluation von endoskopischer Oberflächenrekonstruktion mittels Time-of-Flight-Kameratechnik - Groch, Anja; Hempel, Sarah-Marie; Speidel, Stefanie; Höller, Kurt Emmerich; Engelbrecht, Rainer; Penne, Jochen; Seitel, Alexander; Röhl, Sebastian; Yung, Kwong; Bodenstedt, Sebastian; Pflaum, Felix; Kilgus, Thomas; et al. (Workshop Bildverarbeitung für die Medizin, 2011)
UnivIS-Import:2015-04-16:Pub.2011.tech.IE.LEH.invitr

In Vivo Skin-Type Classification Using Millimeter-Wave Near-Field Probe Spectroscopy - Hecht, Damaris; Pfahler, Tim; Ullmann, Ingrid; Altstidl, Thomas Robert; Amer, Nadia; Jin, Yi; Eskofier, Björn; Vossiek, Martin (2022 52nd European Microwave Conference, 2022)
This paper presents a methodology for millimeter-wave-based in vivo classification of human skin into the two naturally occurring skin types: thick skin with low water content and thin skin with high water content. For medical diagnostic applications in the microwave range, the distinction of the water content plays a major role. The method presented is based on the resonance characteristics of reflective skin measurements. Therefore, in vivo reflective spectra were measured on 10 individuals. For the measurement acquisition, a 3D printed rectangular waveguide-based near-field probe was designed that is sensitive to the skin water content in the frequency range of 75–110 GHz. In total, 360 reflection spectra were obtained, received from six different areas on the hands and arms of the volunteers. A support vector machine (SVM) model with two classes, thick skin on the palm and thin skin present on the arm and back of the hand, was trained with the measured data. The resulting SVM classifier was evaluated to have an accuracy of more than 95%. The high classification accuracy verifies the skin type classification approach as a simple and appropriate in vivo two-level hydration model for the human skin. On the basis of these results, complex challenges such as burn wound classification can become feasible, since ex vivo burn measurements have been shown to display equivalent resonant characteristics.<br

It’s a Match - Scheder, André; Zocher, Nicole; Vossiek, Martin (IEEE Microwave Magazine, 2025)
Antenna impedance tuners are crucial components in modern wireless communication systems, designed to enhance antenna performance and efficiency across a broad frequency range. These devices adjust an antenna’s impedance to align with changing signal environment conditions, thereby maximizing power transfer and minimizing signal reflection. This article explores the design of ultra-low power consumption solid-state impedance tuners specifically for high RF power applications, aligned with the specifications of the Student Design Competition at the International Microwave Symposium 2024 in Washington, DC. The paper delves into the design, simulation, and evaluation processes of an impedance tuner. Additionally, an algorithm is introduced that optimizes tuner states to achieve a high figure of merit for the competition. A high-power test was also conducted to assess the harmonics generated by the tuner and to evaluate its maximum power handling capabilit

It's Tee Time: An Ultrabroadband Componentless Bias Tee: A Planar Ultrabroadband Componentless Bias Tee in Microstrip Line Technology - Kögel, Tobias; Scheder, André; Meyl, Markus; Sohr, Stefan; Vossiek, Martin (IEEE Microwave Magazine, 2024)
With the trend toward ever-higher frequencies and continuously increasing bandwidth in communication for 5G and 6G as well as in the radar domain, the demand on broadband hardware components is rising accordingly [1]. Circuits that were initially considered simple have to be optimized further in order to meet challenging demands.
CRIS-Team Scopus Importer:2024-05-24

Joint Compensation of Frequency Offset, Phase and Amplitude Noise Using Two Stage Extended Kalman Filtering - Pakala, Lalitha; Schmauß, Bernhard (18. ITG-Fachtagung Photonische Netze, 2017)

Joint compensation of phase and amplitude noise using extended Kalman filter in coherent QAM systems - Pakala, Lalitha; Schmauß, Bernhard (40th European Conference on Optical Communication (ECOC), 2014)
We propose and numerically investigate an optimal carrier phase and amplitude noise estimation (CPANE) algorithm using extended Kalman filter (EKF) for effective mitigation of linear and nonlinear phase noise with simultaneous suppression of amplified spontaneous emission (ASE) noise.
lhft_intern.bib::Pakala2014a

Joint Tracking of Polarization State and Phase Noise Using Adaptive Cascaded Kalman Filtering - Pakala, Lalitha; Schmauß, Bernhard (IEEE Photonics Technology Letters, 2017)
We propose a cascaded Kalman filtering (CKF) technique, a series of extended Kalman filter (EKF), and a linear Kalman filter, for joint tracking of phase and amplitude noise as well as polarization state. We further propose an adaptive CKF (A-CKF), in which the process noise covariance has been estimated adaptively, using covariance matching method. Numerical results on back-to-back and transmission scenarios on 28-Gbd polarization-multiplexed 16-quadrature amplitude modulation system justify that our proposed CKF as well as A-CKF outperforms the earlier proposed EKF and the unscented Kalman filter (UKF) with an improved tolerance toward polarization rotations and phase noise besides less computational effor
lhft_intern.bib::Pakala2017f