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Berlt, Philipp; Altinel, Berk; Bornkessel, Christian; Hein, Matthias;
Concept for virtual drive testing on the basis of challenging V2X and LTE link scenarios. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), insges. 5 S.

Virtual drive tests using the over-the-air/vehicle-in-the-loop method are becoming an essential part of testing vehicular radio systems. Different approaches address the question which link scenarios and channel environments are relevant, and should be tested. Up to now, this question has not been fully answered. This paper deals with the identification of challenging scenarios for the wireless transmission standards LTE and ITS-G5 based on jointly performed drive tests, and how these can be transferred into a virtual test concept. In the case of LTE, the focus is on the transition region between different mobile radio cells (cell edge). We have reproducibly observed that the achievable data throughput drops significantly at cell edges compared to the cell centers. For ITS-G5, the communication limit was examined as a function of the distance and visibility conditions between two communicating vehicles.
Schilling, Lisa-Marie; Bornkessel, Christian; Hein, Matthias;
Analysis of instantaneous and maximal RF exposure in 4G/5G networks with dynamic spectrum sharing. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), insges. 5 S.

From mid of 2020 to mid of 2021, the 3G mobile radio network in Germany was gradually replaced by the successor technologies 4G and 5G. Therefore, dynamic spectrum sharing (DSS) was introduced in the 2100 MHz band, which allows a parallel operation of 4G and 5G. There is an increasing need of public information with regard to a possible change in human RF exposure associated with 5G and DSS. Hence, investigations were carried out to study the instantaneous and maximal exposure of persons to base stations in the 2100 MHz band. Our study shows, that the instantaneous exposure has remained comparable before and after the introduction of 4G/5G with DSS. Regarding the maximal RF exposure, code-selective measurements of 3G and 4G with DSS show no significant change in exposure. To analyze the maximal exposure to 5G with DSS, code-selective measurements have been applied for the first time and compared with the 4G exposure in the same band. The results show no significant difference in maximal exposure between 4G and 5G. Furthermore, the need of code-selective measurements in comparison with the frequency-selective method for 5G is demonstrated if different parts of the electromagnetic field that contribute to exposure have to be assigned to selected base stations.
Hasnain, Syed N.; Stehr, Uwe; Stephan, Ralf; Brachvogel, Marius; Meurer, Michael; Hein, Matthias;
Robustness testing of a compact distributed automotive GNSS array in virtual environment. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), insges. 5 S.

To develop a compact distributed array for safe and robust automotive satellite navigation, considerable work on testing prototypes is in progress. Before scheduling resource-hungry outdoor tests, functionality and robustness of a Galileo-compatible compact distributed 4-element L-shaped array receiver has been tested against interference in a virtual environment at E5a frequency band. Such an array consisting of compact quarter wavelength sub-arrays distributed over many wavelengths, fed with a decoupling network, mounted in side mirrors of a mock-up car was measured and evaluated with and without a jammer. The effects of automotive mounting location and robustness of the receiver against the jammer have been analyzed in terms of measured radiation patterns and achieved carrier-to-noise-density ratio of the received satellite signals.
Asghar, Muhammad Ehtisham; Bornkessel, Christian; Stephan, Ralf; Hein, Matthias;
Automotive antenna measurements in the installed state under variable boundary conditions. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), insges. 4 S.

Automotive antenna measurements are typically performed in an anechoic (free-space) or semi-anechoic (reflective ground) environment. Even though measurements under these conditions provide sufficient knowledge about antenna performance, the automotive industry often desires to evaluate installed automotive antennas under practical road conditions. This requires a combined approach to test and qualify vehicular antennas; however, facilities deploying variable boundary conditions for measurements are challenging to devise. Alternatively, numerical simulations can be used to perform such investigations; nevertheless, it is essential to verify such simulations through measurements. In the Virtual Road Simulation and Test Area (VISTA) of the Thuringian Center of Innovation in Mobility at the Technische Universität Ilmenau, a new approach to provide variable boundary conditions for antenna measurements is realized to evaluate the impact of different electromagnetic boundary conditions and to bridge the gap between numerical simulations and measurements. It consists of a modular and mechanically robust plastic frame carrying a customizable fabric substituting a ground plane. This paper presents and discusses the initial measurement results of a reference antenna and an installed automotive antenna performed over the conducting fabric. The convincingly good correlation of more than 74% between the measured data and numerical simulations shows the validity of the proposed method.
Hofmann, Willi; Schwind, Andreas; Bornkessel, Christian; Hein, Matthias;
Analysis of microwave absorber scattering using ray-tracing and advanced measurement techniques. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), insges. 5 S.

Ray-tracing methods can be applied to evaluate the wave propagation in anechoic electromagnetic environments, in order to improve measurement concepts, or to address the increasing demands on test concepts for new radio wireless transmission functionalities. The accuracy of the data obtained from such a chamber model depends crucially on the modeling of the microwave absorbers. Often the scattering off the absorbers is simplified by specular reflections, ignoring the actual direction-dependent scattering properties of the absorbers resulting from their geometry, arrangement, and material. As this may cause significant misconceptions, improved ray-tracing models of absorbers based on their scattering character are needed. In this paper, the scattering of two types of 18″ absorbers with pyramidal and wedge geometries is analyzed and expected scattering patterns are described. Based on an existing shooting-and-bouncing-rays software, a simulation approach is introduced and used to relate the analytical findings with results of measurements of the angle-dependent reflectivity. In addition to the primarily specular reflection for wedge absorbers and scattering in many directions off the pyramidal absorbers, the results show that nearfield effects influence this scattering pattern, as eventually confirmed by the simulations.
Mercier, Mathieu; Mioc, Francesca; Rutkowski, Kim; Scannavini, Alessandro; Nowack, Tobias; Bornkessel, Christian; Hein, Matthias;
Evaluation of integral quantities of over the air automotive antenna measurements. - In: IEEE Xplore digital library, ISSN 2473-2001, (2021), S. 1954-1955

This document outlines the Over the Air (OTA) testing methodology which is currently employed for full automotive antennas and provides a pertinent Figure of Merit.
Tayyab, Umais; Kumar, Ashish; Li, Yihan; Stephan, Ralf; Hein, Matthias; Singh, Jasmeet;
Plastic-embedded patch antenna array for automotive satellite communication in the Ka-band. - In: IEEE Xplore digital library, ISSN 2473-2001, (2021), S. 1-4
Solomitckii, Dmitrii; Heino, Mikko; Buddappagari, Sreehari; Hein, Matthias; Valkama, Mikko;
Radar scheme with raised reflector for NLOS vehicle detection. - In: IEEE transactions on intelligent transportation systems, (2021), S. 1-9
Early access

The employment of passive reflectors enables the millimeter-wave automotive radars to detect an approaching vehicle in non-line-of-sight conditions. In this paper, the installation of such reflectors above the sidewalk at an intersection is proposed and studied, avoiding pedestrians' blockage and road dust effect at ground level. Through the analysis of the backscattering power, it is shown that the suggested scheme may detect an approaching vehicle in the blind zone at distances of 30,łdots,50 m to the intersection point. Additionally, the analysis shows that efficient operation is highly dependent on the spatial orientation and size of the reflector. Even a few degrees rotation may change the detecting range by several meters. In turn, the larger area of the reflector may cover longer detecting distances, improving the radar scheme's overall performance. It is also shown that further performance enhancement can be achieved by employing a C-type radar, contributing an extra 5 dB to the backscattering power relative to an A-type radar. However, despite these improvements, the strongest scattering centre of the detectable vehicle is systematically identified to the bumper zone.
Hein, Matthias; Stephan, Ralf; Buddappagari, Sreehari; Asghar, Ehtisham;
Systemvalidierung von Fahrzeugradaren mittels drahtloser Techniken - SafeMove : Schlussbericht der TU Ilmenau zum F&E-Verbundvorhaben : Laufzeit des Vorhabens: 01.01.2017-30.09.2020. - [Ilmenau] : [Technische Hochschule Ilmenau, Thüringer Innovationszentrum Mobilität]. - 1 Online-Ressource (36 Seiten, 5,73 MB)Förderkennzeichen BMBF 16ES0547K
Hofmann, Willi; Schwind, Andreas; Bornkessel, Christian; Hein, Matthias;
Bi-static reflectivity measurements of microwave absorbers between 2 and 18 GHz. - In: IEEE Xplore digital library, ISSN 2473-2001, (2021), insges. 6 S.

In anechoic chambers, the level of spurious reflections is determined by the reflectivity of the installed absorbers and is usually estimated using ray-tracing methods. But since the basic assumption of a purely specular reflection in most of these ray-tracing methods can lead to insufficient results, the reflectivity of the absorbers must be analyzed for oblique incidence and over a broad range of observation angles. In this paper, a bi-static measurement setup is proposed, which overcomes angular limits of the NRL-arch method and allows to analyze the scattering behavior of absorbers in an extended angular range. Using this setup, and applying the radar cross-section method, the reflectivity of two types of pyramidal absorbers was analyzed with respect to different illumination and observation angles for parallel and perpendicular polarization between 2 and 18 GHz. While the measurement results for normal incidence agree well with the specifications, additional non-specular reflections of similar strength were detected in the time-domain at different observation angles. Especially for the case of oblique wave incidence, it becomes apparent that the highest reflectivity does not necessarily occur for specular reflection. These findings help to improve the understanding of the scattering behavior of absorbers in general, as more comprehensive analyses become possible with this method.