Hybrid measurement and post-processing method for human RF exposure assessment of mobile radio small-cells. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
Established methods for determining the electromagnetic field exposure of mobile radio small-cell base stations to the general public are currently based either on numerical far-field computation or on field strength measurement at selected evaluation points. It means that they are not capable of providing a realistic 3-dimensional near-and far-fleld evaluation of mobile radio small-cell base stations. For this reason, a promising hybrid exposure assessment approach - which combines antenna nearfield pattern measurements and numerical computations under varying environmental conditions - was specially adapted to small cells. While the conservatively determined measurement uncertainty of ± 3 dB is comparable to already established methods such as electric field probe measurement, the hybrid assessment offers novel possibilities in terms of flexibility. By moving exposure assessment into a virtual domain, complex installation scenarios or varying antenna operation parameters can typically be investigated within a simulation environment, so that complex measurement campaigns may be substituted by hybrid assessment.
https://doi.org/10.23919/EuCAP57121.2023.10133468
Receiver bandwidth extension beyond Nyquist using channel bonding. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
Current and upcoming communication and sensing technologies require ever larger bandwidths. Channel bonding can be utilized to extend a receiver’s instantaneous bandwidth beyond a single converter’s Nyquist limit. Two potential joint front-end and converter design approaches are theoretically introduced, realized and evaluated in this paper. The Xilinx RFSoC platform with its 5 GSa/s analog to digital converters (ADCs) is used to implement both a hybrid coupler based in-phase/quadrature (I/Q) sampling and a time-interleaved sampling approach along with channel bonding. Both realizations are demonstrated to be able to reconstruct instantaneous bandwidths of 5 GHz with up to 49 dB image rejection ratio (IRR) typically within 4 to 8 dB the front-ends’ theoretical limits.
https://doi.org/10.23919/EuCAP57121.2023.10133262
Antennas for railway applications: comparison between scaled mock-up and real locomotive measurements. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
This paper presents and compares real locomotive and scaled mock-up antenna measurements to investigate the reliability of scaled model measurements and to evaluate the impact of the locomotive chassis on the performance of the installed antennas. Three different operational frequencies and two distinct mounting positions at the center and front of the locomotives were selected for comparison. Fair comparability between patterns is observed with a similarity factor above 64%. The deviations between patterns arise from different geometries and installed superstructures. However, the results reveal coherent findings, particularly the significant impact of locomotive chassis, roof geometries, and superstructures on the radiation patterns. This impact becomes more pronounced at higher frequencies. Moreover, the front position results show strong distortions in patterns compared to the center position. The results imply that when analyzing the installed locomotive antenna pattern beside the chassis, the impact of superstructures and the impact of the mounting position must be carefully considered.
https://doi.org/10.23919/EuCAP57121.2023.10133303
Measurement testbed for radar and emitter localization of UAV at 3.75 GHz. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
This paper presents an experimental measurement platform for the research and development of unmanned aerial vehicles (UAVs) localization algorithms using radio emission and reflectivity. We propose a cost-effective, flexible testbed made from commercial off-the-shelf (COTS) devices to allow academic research regarding the upcoming integration of UAV surveillance in existing mobile radio networks in terms of integrated sensing and communication (ISAC). The system enables nanosecond-level synchronization accuracy and centimeter-level positioning accuracy for multiple distributed sensor nodes and a mobile UAV-mounted node. Results from a real-world measurement in a 16 km^2 urban area demonstrate the system’s performance with both emitter localization as well as with the radar setup.
https://doi.org/10.23919/EuCAP57121.2023.10133118
Optimized assessment procedure for maximal RF exposure to 5G massive MIMO base stations in non-line-of-sight scenarios - part 2: verification by field measurements. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
At measurement points (MP) with a line of sight (LOS) to the base station, measurement and extrapolation procedures already exist to determine the maximal exposure in the vicinity of 5G massive MIMO base stations. However, for MPs with non-LOS (NLOS) to the base station, incorrect estimations of the maximal exposure have been found. Based on the theoretical preliminary considerations in part 1 of this paper, the exposure at outdoor NLOS MPs has been determined at 63 MPs in the vicinity of seven Huawei base stations. The gain correction factors previously used by assuming free-space propagation have been compared with the actual gain correction factors derived from the measurements. It is shown that the resulting misestimation and the actual gain correction factors depend on the distance between the MP and the base station. On the basis of this, generalised extrapolation factors are derived for NLOS MPs. Theoretical and numerical investigations are explained in detail in the accompanying paper "part 1".
https://doi.org/10.23919/EuCAP57121.2023.10133149
Optimized assessment procedure for maximal RF exposure to 5G massive MIMO base stations in non-line-of-sight scenarios - part 1: theoretical and numerical investigations. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
The evaluation of the maximal human RF exposure to 5G base stations acquires a specific extrapolation procedure due to the massive MIMO antennas. Up to now, large misestimations of up to 15 dB of the extrapolated maximal RF exposure compared to the reference value were found at measurement points under non-line-of-sight conditions. One possible cause is the incorrectly determined gain correction factor based on free space assumptions which is used for extrapolating the measured signalization exposure to the maximal possible exposure. This gain correction factor may differ greatly between line-of-sight and non-line-of-sight scenarios. In this paper, considerations based on geometrical optics are used to identify such causative scenarios. Here, the measurement points are in multipath environments, where the resulting field distributions and the corresponding gain correction factors are not identical compared to the free space. Numerical simulations with ray tracing confirm this assumption as the determined gain correction factor in the multipath scenario is significantly lower compared to the free space case. Verification of these considerations by measurement is done in the accompanying paper "Part 2".
https://doi.org/10.23919/EuCAP57121.2023.10133658
Spatial/temporal characterization of propagation and blockage from measurements at sub-THz in industrial machines. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
In the present paper we introduce novel ultra-wideband (UWB) dual-polarized double-directional measurements at sub-THz (300 GHz) in an access point to inside of machine application in an industrial scenario. The results show a sparse spatial/temporal channel with multiple paths from the different metallic objects and their influence on polarization. In addition, different LOS blockage situations were investigated, showing the presence of alternative paths for communications.
https://doi.org/10.23919/EuCAP57121.2023.10133323
Measurement-based analysis of multi-band assisted beam-forming at mmWave in industrial scenarios. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
The mmWave and sub-THz bands are foreseen as candidates to achieve the data-rate demands in the beyond 5G and 6G wireless communication networks. The co-existence of multiple radio interfaces at several bands enables data fusion and the utilization of the similarities and differences on propagation and system properties for communication and sensing applications. MmWave radio interfaces rely on directive beams that require high training overhead for beam steering. Sensors in the network infrastructure and co-located radio interfaces at sub-6 GHz and mmWave can be used to assist the beam-forming process at mmWave. In the present paper we investigate the performance of multi-band assisted beam-forming in an industrial environment. We empirically demonstrate from real-world measurements that even in NLOS, the direction of the beams estimated at sub-6 GHz can be used to established a link at mmWave.
https://doi.org/10.23919/EuCAP57121.2023.10133694
Reduction of mutual coupling between dual-polarized antenna elements using defected ground structures. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
To accurately model a communication channel using channel sounding technique, having dual-polarized antenna elements and low mutual coupling between them is required. In this work a Defected Ground Structure (DGS) is proposed to reduce the mutual coupling between two dual polarized mmWave antenna elements in an array structure. The defected ground is made of etched C-shape slots. The presence of the DGS has a strong impact on H-plane coupling where a suppression of 35 dB is achieved, while the reduction of E-plane coupling is about 4 dB. The unwanted effect on the radiation patterns is negligible and the back radiation is not increased.
https://doi.org/10.23919/EuCAP57121.2023.10133636
Deep learning based anomaly detection for visual inspection on the industrial dataset. - Ilmenau. - 64 Seiten
Technische Universität Ilmenau, Masterarbeit 2023
Die Erkennung von Anomalien in visuellen Inspektionssystemen ist entscheidend um die Qualitätskontrolle und Sicherheit in verschiedenen Industriezweigen zu gewährleisten. Deep Learning basierende Techniken haben vielversprechende Ergebnisse bei der Erkennung anomaler Daten in industriellen Datensäetzen geliefert. In dieser Masterarbeit haben wir einen neuartigen Ansatz untersucht, der auf unüberwachtem Lernen basiert unter Verwendung von Convolutional Autoencodern. Das Ziel war die Erkennung von Anomalien im Montageprozess der Fertigungshalle. Zusäetzliche wurde Yolov5 verwendet um die Kameraaufnahmen füer eine bessere Anomalierkennung aufzubereiten. Die vorliegende Arbeit untersucht die Durchführbarkeit von unüeberwachtem Lernen auf dem industriellen Datensatz und vergleicht ihn mit überwachten Lerntechniken, die an gelabelte, beschriftete Daten gebunden sind und somit erhebliche Kosten verursachen. Die bearbeiteten Forschungsfragen lauteten: (1) Können Convolutional Autoencoder effektiv Anomalien erkennen, (2) was sind die zugrunde liegenden Mechanismen, die unüeberwachte Lerntechniken effektiver bei der Erkennung von Anomalien machen als üeberberwachte Lerntechniken (3) Was sind die möglichen Grenzen und Weiterentwicklungsmöglichkeiten des vorgeschlagenen Ansatzes ? Die Ergebnisse der Arbeit zeigen, dass die Verwendung von Convolutional Autoencoder für die Erkennung von Anomalien eine wirksame Strategie für die visuelle Inspektion ist. Die Überlegenheit des unüberwachten Lernens bei der Erkennung von Anomalien ist auf seine Fähigkeit zurückzuführen, die Struktur und Muster der Daten zu erfassen und auf neue Instanzen von anomalem Daten zu reagieren. Der vorgeschlagene Ansatz erzielte eine hohe Präzision, Recall und F1-Score. Die Einschränkungen und potenziellen Bereiche für Verbesserungsmöglichkeiten liegen in der weiteren Optimierung und Validierung mit größeren Datenmengen. Insgesamt hat der Ansatz ein enormes Potenzial zur Verbesserung bestehender Verfahren der Anomalieerkennung in visuellen Inspektionssystemen.