Bi-static delay-Doppler reference for cooperative passive vehicle-to-X radar applications. - In: IET microwaves, antennas & propagation, ISSN 1751-8733, Bd. 14 (2020), 14, S. 1749-1757
Automotive radar systems are indispensable for advanced driver assistance systems and traffic safety. Besides existing monostatic radar techniques, bi-static radar sensing like passive coherent location offers additional options to improve the radar visibility of vulnerable road users. Regarding the testing and evaluation of signal processing algorithms including parameter estimation, it is essential to provide electromagnetically shielded and reproducible measurement conditions, in addition to field tests in real traffic scenarios. This study describes the possibility to emulate relevant performance parameters for bi-static radar scenarios in the frequency range from 1 GHz to 6 GHz in a metal-shielded semi-anechoic chamber. Of special interest are the bi-static angle between transmitter, target, and receiver, and the resulting bi-static Doppler frequencies of a realistic vehicular traffic scenario. According to the concept of cooperative passive coherent location, Doppler scattering measurements are presented and compared to electromagnetic simulations. The authors find promising agreement between measured and ground truth data in the delay-Doppler spectrum.
https://doi.org/10.1049/iet-map.2019.0991
Hardware architecture for ultra-wideband channel impulse response measurements using compressed sensing. - In: 28th European Signal Processing Conference (EUSIPCO 2020), (2020), S. 1663-1667
We propose a compact hardware architecture for measuring sparse channel impulse responses (IR) by extending the M-Sequence ultra-wideband (UWB) measurement principle with the concept of compressed sensing. A channel is excited with a periodic M-sequence and its response signal is observed using a Random Demodulator (RD), which observes pseudo-random linear combinations of the response signal at a rate significantly lower than the measurement bandwidth. The excitation signal and the RD mixing signal are generated from compactly implementable Linear Feedback Shift registers (LFSR) and operated from a common clock. A linear model is derived that allows retrieving an IR from a set of observations using Sparse-Signal-Recovery (SSR). A Matrix-free model implementation is possible due to the choice of synchronous LFSRs as signal generators, resulting in low computational complexity. For validation, real measurement data of a time-variant channel containing multipath components is processed by simulation models of our proposed architecture and the classic M-Sequence method. We show successful IR recovery using our architecture and SSR, outperforming the classic method significantly in terms of IR measurement rate. Compared to the classic method, the proposed architecture allows faster measurements of sparse time-varying channels, resulting in higher Doppler tolerance without increasing hardware or data stream complexity.
https://doi.org/10.23919/Eusipco47968.2020.9287454
Characterization of GPS disciplined oscillators using a laboratory GNSS simulation testbed. - In: IEEE IFCS-ISAF 2020, (2020), insges. 4 S.
This paper introduces a testbed to characterize the performance of GPS disciplined oscillators using a GNSS signal simulator and a measurement system based on software-defined radios and digital signal processing that allows to examine the stability of up to four devices with sub-nanosecond precision, time-coherently for 1 PPS and 10 MHz signals, in a controllable laboratory environment with reproducible and adjustable GNSS signal settings over a long-term observation period. To demonstrate the effectiveness of this method, four devices of one specific low-cost GPSDO type available to the authors are characterized and compared in terms of their positional accuracy and their time and frequency stability in steady state and during stabilization.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234932
Stochastic modeling of short and long term clock skew. - In: IEEE IFCS-ISAF 2020, (2020), insges. 4 S.
Traditional black box clock skew models are either the power-law noise model or a more recent approach based on auto-regressive (AR) filters. Unfortunately, neither algorithm can accurately model short and long term skew due to limited degrees of freedom or stability constraints. We propose a novel model that employs the current AR algorithm recursively with appropriate pre- and post-processing to achieve numeric stability and accurate reproduction of short and long term effects. The model coefficients are derived from a measured skew signal, with the model output matching an exemplary original signal closely in terms of Allan variance and time-domain behavior.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234818
Characterizing GPS disciplined oscillators for distributed vehicle-to-X measurement applications. - In: IEEE IFCS-ISAF 2020, (2020), insges. 4 S.
In this paper, we analyze the reference signal stability of 1 PPS and 10 MHz signals provided by a low-cost GPS disciplined oscillator under application specific conditions using a comparable light-weight measurement system based on software defined radio and digital signal processing. In mobile measurement scenarios, GPS signal impairments are inevitable, due to obstacles such as buildings, street canyons, bridges, and tunnels. Therefore, we preliminarily characterize four GPSDOs under test in a stationary setup using controlled GPS reception loss to drive them into alternating operation modes, namely free-run, disciplined and holdover mode. Further, we conducted a more than 100 km real-world diversified test drive to characterize the performance of the particular GPSDO as realistically as possible for the intended use in mobile V2X measurements.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234915
Acoustic process monitoring in laser beam welding. - In: 11th CIRP Conference on Photonic Technologies [LANE 2020], (2020), S. 763-768
Structure-borne acoustic emission (AE) measurement shows major advantages regarding quality assurance and process control in industrial applications. In this paper, laser beam welding of steel and aluminum was carried out under varying process parameters (welding speed, focal position) in order to provide data by means of structure-borne AE and simultaneously high-speed video recordings. The analysis is based on conventionally (e.g. filtering, autocorrelation, spectrograms) as well as machine learning methods (convolutional neural nets) and showed promising results with respect to the use of structure-borne AE for process monitoring using the example of spatter formation.
https://doi.org/10.1016/j.procir.2020.09.139
OFDM waveform for distributed radar sensing in automotive scenarios. - In: International journal of microwave and wireless technologies, ISSN 1759-0795, Bd. 12 (2020), 8, S. 716-722
https://doi.org/10.1017/S1759078720000859
eadf: representation of far-field antenna responses in Python. - In: SoftwareX, ISSN 2352-7110, Bd. 12 (2020), 100583, S. 1-6
https://doi.org/10.1016/j.softx.2020.100583
Measurement campaign with synchronized distributed receivers and mobile emitter at 3.75 GHz in urban scenarios. - In: 2020 IEEE 91st Vehicular Technology Conference (VTC Spring), (2020), insges. 5 S.
https://doi.org/10.1109/VTC2020-Spring48590.2020.9128562
Performance of OFDMA resource scheduling in joint mobile radio and radar networks. - In: 14th European Conference on Antennas and Propagation, (2020), insges. 5 S.
https://doi.org/10.23919/EuCAP48036.2020.9135864