Characterization of GPS disciplined oscillators using a laboratory GNSS simulation testbed. - In: IEEE Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (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
Measurement of drift and jitter of network synchronized distributed clocks. - In: IEEE Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (2020), insges. 8 S.
We propose a measurement setup for simultaneous measurement of drift and jitter of network synchronized distributed clocks using only off-the-shelf components. A network interface card with hardware timestamping capability and a local GPS-synchronized PTP grandmaster combined with appropriate post-processing enable absolute time measurement with sub-microsecond accuracy. The setup is explained in detail and its use exemplified by a 34 day measurement campaign. By polling a selection of globally distributed, GPS-synchronized NTP servers, delay asymmetry measurements were enabled. A detailed analysis of results illustrates the time-variant statistical properties of the jitter.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234926
Stochastic modeling of short and long term clock skew. - In: IEEE Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (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 Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (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: Procedia CIRP. - Amsterdam [u.a.] : Elsevier, ISSN 2212-8271, Bd. 94 (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. - Cambridge : Cambridge Univ. Press, 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. - Amsterdam [u.a.] : Elsevier, 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: IEEE Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (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: IEEE Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (2020), insges. 5 S.
https://doi.org/10.23919/EuCAP48036.2020.9135864
Multi-band characterization of propagation in industry scenarios. - In: IEEE Xplore digital library. - New York, NY : IEEE, ISSN 2473-2001, (2020), insges. 5 S.
https://doi.org/10.23919/EuCAP48036.2020.9135630