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Item type:Publication, Access status: with files , Antenna setup for future joint radar-communications - characteristics and mounting positions(Copernicus Publications, 2023-03-21); ; ; ; The development of millimeter wave systems is driven by the strong trend toward new communications generations and especially by the emerging joint radar and communications design approach. Safety-critical applications like platooning or intersection assistance will significantly benefit from the combination of sensing and communications. While radar performs a channel measurement and thus, needs a wide field of view (especially in city/intersection scenarios), communications aims to minimize the interference for other not addressed receivers (e. g. in a platoon) by a focused antenna design. The proposed work extends the analysis of the influence of various antenna positioning for a typical automotive scene by taking also different characteristics (antenna gain, half power beamwidth, and sidelobe level) into account. Hereby, it is mandatory to investigate the communications and sensing performance simultaneously. The positions at the front bumper - typical for radar sensors - and especially at the left mirror convinced regarding the vehicular communications as well as the sensing behaviour. Applying focused antennas is promising, however, has also limits if the signals are not received out of the main beam but out of the sidelobes, resulting in a critical communications performance. Thus, beam steering is recommended to be applied in the future.Publicationtype: Journal ArticleScopus© Citations 1 76 94 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A 10 kHz to 6 GHz low-cost vector network analyzer(Copernicus Publications, 2021-12-17); ; ; This publication introduces a low-cost vector network analyzer with very large frequency range made of commercial off-the-shelf components. It utilizes two identical receivers and two directional bridges to allow for two fully bidirectional measurement ports. The design surpasses the performance of competing low-cost network analyzers in regards of dynamic range, frequency span and calibration capability.Publicationtype: Journal ArticleScopus© Citations 1 147 323 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A 24 GHz waveguide based radar system using an advanced algorithm for I/Q offset cancelation(Copernicus Publications, 2017-10-25); ; ; ; Precise position measurement with micrometer accuracy plays an important role in modern industrial applications. Herewith, a guided wave Six-Port interferometric radar system is presented. Due to limited matching and discontinuities in the radio frequency part of the system, the designers have to deal with DC offsets. The offset voltages in the baseband lead to worse relative modulation dynamics relating to the full scale range of the analog-To-digital converters and thus, considerably degrade the system performance. While common cancelation techniques try to estimate and extinguish the DC offsets directly, the proposed radar system is satisfied with equalizing both DC offsets for each of the two differential baseband signal pairs. Since the complex representation of the baseband signals is utilized for a subsequent arctangent demodulation, the proposed offset equalization implicates a centering of the in-phase and quadrature (I/Q) components of the received signal, which is sufficient to simplify the demodulation and improve the phase accuracy. Therefore, a standard Six-Port radar system is extended and a variable phase shifter plus variable attenuators are inserted at different positions. An intelligent algorithm adjusts these configurable components to achieve optimal I/Q offset cancelation.Publicationtype: Journal Article224 172 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Design and analysis of ultra-wideband antennas for transient field excitationsThis work addresses the design of two ultrawideband antennas for the application of transient field measurements that are characterized by frequency spectra that typically range from a few MHz to several GHz. The motivation for their design is the excitation of high power transient pulses, such as double exponential or damped sinusoidal pulses, within highly resonant metallic enclosures. The antenna design is based on two independent numerical full-wave solvers and it is aimed to achieve a low return loss over a wide range of frequencies together with a high pulse fidelity. It turns out that antennas of the conical and discone type do achieve satisfactory broadband characteristics while limitations towards low frequencies persist. Also the concept of fidelity factor turns out as advantageous to determine whether the proposed antennas allow transmitting certain broadband pulse forms.Publicationtype: Journal ArticleScopus© Citations 1 277 276 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Numerical computation of lightning transfer functions for layered, anisotropically conducting shielding structures by the method of moments(Copernicus Publications, 2016-09-28); ; ; A formalism for the computation of lightning transfer functions by the method of moments, which involves shielding structures that may consist of layered, anisotropically conducting composite materials, is presented in this contribution. The composite materials, being of a type that is widely used in space- and aircraft design, are electrically characterized by an equivalent conductivity. As basis for the quantitative analysis the method of moments is used where shielding surfaces can be treated by a thin layer technique which utilizes analytical solutions inside the layer. Also the effect of an extended lightning channel can be taken into account. The method is applied to geometries that resemble an actual airplane fuselage.Publicationtype: Journal ArticleScopus© Citations 1 296 339 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Frequency versus time domain immunity testing of Smart Grid componentsSmart Grid components often are subject to considerable conducted current disturbances in the frequency range 2-150 kHz and, as a consequence, it is necessary to provide reliable immunity test methods. The relevant basic standard IEC 61000-4-19 that is currently under discussion focusses on frequency domain test methods. It is remarked in this contribution that in the context of frequency domain testing the chosen frequency spacing is related to the resonance response of the system under test which, in turn, is characterized in terms of resonance frequencies and quality factors. These notions apply well to physical system but it is pointed out by the example of an actual smart meter immunity test that smart grid components may exhibit susceptibilities that do not necessarily follow a resonance pattern and, additionally, can be narrowband. As a consequence it is suggested to supplement the present frequency domain test methods by time domain tests which utilize damped sinusoidal excitations with corresponding spectra that properly cover the frequency range 2-150 kHz, as exemplified by the military standard MIL-STD-461.Publicationtype: Journal ArticleScopus© Citations 1 269 248 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Single-element based ultra-wideband antenna array concepts for wireless high-precision 2-D local positioning(Copernicus Publications, 2013-09-03); ; ; We generally categorize the approaches for ultrawideband antenna array design, and consequently propose simplified concepts for antenna arrays for a high-precision, ultra-wideband FMCW radar 2-D local positioning system to obtain robustness against multi path interference, perform angle of arrival analysis, as well as instantaneous heading estimation. We focus on low-cost and mechanical robust, industrial-application ready antennas. The antenna arrays are optimized for operation in the 5 GHz to 8 GHz frequency range and are designed towards supporting full omnidirectional 360° as well as partial half-plane direction of arrival estimation. Two different concepts for vehicle- as well as wall-mounted antenna array systems are proposed and discussed. We propose a wideband unidirectional bow-tie antenna array element having 97%impedance and 37%pattern bandwidth and a robust vehicle mounted omnidirectional antenna element having more than 85% impedance and pattern bandwidth.Publicationtype: Journal ArticleScopus© Citations 1 194 199 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Dead time optimization method for power converterThis paper introduces a method for dead time optimization in variable speed motor drive systems. The aim of this method is to reduce the conduction time of the freewheeling diode to a minimum without generation of cross conduction. This results in lower losses, improved EMC, and less overshooting of the phase voltage. The principle of the method is to detect beginning cross currents without adding additional components in the half bridge like resistors or inductances. Only the wave shape of the phase voltage needs to be monitored during switching. This is illustrated by an application of the method to a real power converter.Publicationtype: Journal ArticleScopus© Citations 3 308 348 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Accelerating the numerical computation of indirect lightning effects by means of vector fitting(U.R.S.I.-Landesausschuss in der Bundesrepublik Deutschland e.V., 2011-08-01); In the context of numerical computation of indirect lightning effects it is customary to use volume-discretizing methods in time domain, such as the Finite Difference Time Domain (FDTD) method, the Finite Integration Technique (FIT), or the Transmission Line Matrix (TLM) method. If standard lightning electromagnetic pulses (LEMPs) of tenths of microseconds duration are used as excitations, these methods require long computation times, as implied by the Courant criterion. It is proposed to use shorter pulse forms and to compare the transfer functions obtained by different pulse durations by means of macromodels that are obtained from the vector fitting method. Numerical computation of lightning related transfer functions of a canonical structure indicate that the duration of the exciting pulse can typically be shortened by at least one order of magnitude if compared to a standard pulse. © 2011 Author(s) CC Attribution 3.0 License.Publicationtype: Journal ArticleScopus© Citations 2 274 248 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Untersuchung der Einkopplungen von UWB-Pulsen auf Funksysteme im 2,4-GHz-ISM-BandDieser Bericht fasst die durchgeführten Messungen zur Abschätzung möglicher Kopplung elektromagnetischer Energie ausgehend von abgestrahlten UWB-Pulsen auf Funkübertragungssysteme im 2,4-GHz-ISM-Band zusammen. Dabei wird genauer auf die sogenannte Frontdoor- und Backdoorkopplung eingegangen. Während für die Abschätzung der Frontdoorkopplung generische PCB-Antennen untersucht wurden, sind für die Backdoorkopplung Standard-USB-Funkmodule zum Einsatz gekommen. Es wird im Gesamten eine Abschätzung gegeben, inwieweit UWB-Pulse Funkübertragungssysteme beeinflussen können. Die durchgeführten Messungen wurden mit Hilfe einer GTEM-Zelle in Verbindung mit dem UWB-Pulsgenerator PBG3 der Firma Kentech durchgeführt. Weiterhin sind die Auswirkungen von UWB-Pulsen auf ein reales Funkübertragungssystem im 2,4-GHz-ISM-Band untersucht worden.Publicationtype: Journal Article272 311