Dual-band nested circularly polarized antenna array for 5G automotive satellite communications. - In: Applied Sciences, ISSN 2076-3417, Bd. 13 (2023), 21, 11915, S. 1-15
Currently, 5G low-earth orbit satellite communications offer enhanced wireless coverage beyond the reach of 5G terrestrial networks, with important implications, particularly for automated and connected vehicles. Such wireless automotive mass-market applications demand well-designed compact user equipment antenna terminals offering non-terrestrial jointly with terrestrial communications. The antenna should be low-profile, conformal, and meet specific parameter values for gain and operational frequency bandwidth, tailored to the intended applications, in line with the aesthetic design requirements of passenger cars. This work presents an original concept for a dual-band nested circularly polarized automotive user terminal that operates at the S-band frequencies around 3.5 GHz and Ka-band frequencies around 28 GHz, namely within the 5G new-radio bands n78 and n257, respectively. The proposed terminal is designed to be integrated into the plastic components of a passenger vehicle. The arrays consist of 2 × 2 aperture-coupled corner-truncated microstrip slot patch antenna elements for the n78 band and of 4 × 4 single-layer edge-truncated microstrip circular slot patch antenna elements for the n257 band. The embedded arrays offer, across the two bands, respectively, 9.9 and 13.7 dBi measured realized gain and 3-dB axial ratio bandwidths of 100 and 1500 MHz for the n78 and n257 bands along the broadside direction. Detailed link budget calculations anticipate uplink data rates of 21 and 6 Mbit/s, respectively, deeming it suitable for various automotive mobility and Internet-of-Things applications.
https://doi.org/10.3390/app132111915
Suitability of dual-band, dual-polarized patch antennas with a superstrate for the miniaturization of Ku-band antenna arrays for automotive applications. - In: Applied Sciences, ISSN 2076-3417, Bd. 13 (2023), 19, 10867, S. 1-13
The extension of low-earth orbit (LEO) services to non-terrestrial mobile communications has huge potential for eliminating network white spots and providing high-speed, low-latency links with worldwide geographic coverage. State-of-the-art user terminals for mobile platforms are too large for integration into a passenger vehicle. Antenna elements loaded with a dielectric superstrate could potentially lead to a considerable miniaturization of the user terminal. As per link budget calculations, an array with a gain of 27 dBi is necessary to ensure a throughput of 25 Mbps in the downlink at the Ku-band. A conventional array with a gain of 6 dBi per element, assuming a 12 × 12 arrangement with half-wavelength spacing, would require a footprint of 36 λ2 at 10 GHz to achieve this target and appears unsuitable for automotive integration. This paper proposes a low-profile, dual-band, dual-polarized, vertically stacked patch antenna with superstrate loading and shows that the inclusion of the superstrate improves the antenna’s gain by at least 3 dB. Therefore, compared to a conventional array, a superstrate-loaded array would need only half of the number of elements to meet the target gain, thus occupying only half of the surface area, and offers better integration for automotive applications. Requiring half of the number of elements also implies considerably reduced design complexity and cost.
https://doi.org/10.3390/app131910867
Fingerprints of the automotive radar scattering of passenger cars and vans. - In: Applied Sciences, ISSN 2076-3417, Bd. 13 (2023), 18, 10290, S. 1-12
The radar scattering characteristics of extended objects are an important parameter for perception and tracking algorithms in automated driving tasks. Therefore, high-fidelity sensor models are required to simulate and evaluate typical driving scenarios in virtual testing applications. While the general analysis of typical scattering centers of passenger cars is well studied, there are only a few publicly available reports that analyze specific features of the scattering characteristics of different vehicle types. Hence, this work presents detection distributions derived from systematic measurements for six different vehicle types, conducted with a commercial automotive radar on a proving ground. In particular, the contribution of underbody reflections to the respective radar signatures is analyzed, which are caused by multipath propagation via the road surface. The measurements reveal distinctive differences between the scattering characteristics of different vehicles, which are attributed to the respective underbody geometry.
https://doi.org/10.3390/app131810290
Metal surface tolerant conformal low-profile plastic embedded antennas for automotive applications. - Ilmenau : Universitätsbibliothek, 2023. - 1 Online-Ressource (xiii, 110 Seiten)
Technische Universität Ilmenau, Dissertation 2023
Mit der rasanten Zunahme drahtloser Dienste und dem Einsatz von Antennendiversitätstechniken zur Erzielung höherer Datenraten oder Dienstzuverlässigkeit ist die Zahl der in Pkw zu installierenden Antennen nicht mehr unbedeutend und nimmt weiter zu. Gleichzeitig wird es immer schwieriger, geeignete Montageplätze für diese Antennen zu finden, da die Zahl der Montageplätze im Auto nicht parallel zur Zahl der zu installierenden Antennen gewachsen ist; Autos sind nach wie vor meist Metallkästen, mit einigen wenigen Kunststoffteilen und Glasscheiben die die Integration von Antennen ermöglichen. Die meisten dieser Teile wurden bereits zu diesem Zweck verwendet, die B-Säulen-Kunststoffabdeckungen wurden jedoch bisher nicht für die Antennenintegration berücksichtigt. In dieser Arbeit werden nicht nur die Vorteile der B-Säulen-Kunststoffabdeckungen als Antenneneinbauort gegenüber anderen Orten hervorgehoben, sondern auch die damit verbundenen Herausforderungen untersucht, insbesondere der begrenzte Platz für die Antennenintegration und die unmittelbare Nähe der eingebauten Antenne zum Metallchassis des Fahrzeugs. Letzteres führt zu einer starken elektromagnetischen Kopplung zwischen der Antenne und der Fahrzeugkarosserie, was sich auf die Antenneneigenschaften wie Impedanzanpassung und realisierten Gewinn auswirkt. In den folgenden Kapiteln werden die zugrundeliegenden Entwurfsprinzipien, die Theorie und die Messungen neuartiger, flacher, konformer und metalloberflächentoleranter Mobilfunkantennen vorgestellt, nämlich die Einzelband-Di-Patch-Antenne und eine koplanar gestapelte, mit Mikrostreifenleitungen gekoppelte Multibandantenne, die die oben genannten Herausforderungen adressieren und überwinden. Zusätzlich wird in der zweiten Hälfte dieser Arbeit eine high impedance surface basierte Dipolantennenlösung vorgestellt. Die Simulations- und Messergebnisse der nicht integrierten und der integrierten Versionen der vorgestellten Antennen, einschließlich der LTE-MIMO-Datenratenmessungen, die im vorletzten Kapitel vorgestellt werden, sprechen nicht nur für die Eignung dieser Antennen für flache, metallnahe Oberflächenanwendungen im Allgemeinen, sondern zeigen auch, dass die B-Säulen- Kunststoffabdeckungen einen sehr geeigneten neuen Antennenintegrationsort für mobile Kommunikationsanwendungen im Automobil darstellen.
https://doi.org/10.22032/dbt.57612
Space-time adaptive processing as a solution for mitigating interference using spatially-distributed antenna arrays. - In: Navigation, ISSN 2161-4296, Bd. 70 (2023), 3, navi.592, insges. 23 S.
Antenna arrays and spatial processing techniques are among the most effective countermeasures against interference. Here, we demonstrate a new array concept consisting of spatially-distributed subarrays that are small enough to fit inside the non-metallic parts of an automobile. This will facilitate concealed installation of these devices in bumpers or side mirrors, which is a strict requirement of the industry and preferred by the customers. Using beamforming algorithms, this array was proven to be robust against jammers in the L1 band. The large distances between the individual antenna elements resulted in a non-negligible baseband delay that violated the narrowband assumption and increased with bandwidth. Hence, this paper demonstrates the influence of a jammer in the L5 band. Space-time adaptive processing that allows for compensation of the delays was introduced and analyzed. Improvements in interference mitigation capabilities were assessed and compared to those of pure spatial state-of-the-art implementation. Real-life measurement data was used to ensure realistic results.
https://doi.org/10.33012/navi.592
Emulation of realistic satellite constellations for GNSS receiver testing in virtual environment. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
Automotive navigation is key for modern traffic, which necessitates robust satellite navigation receivers. Distributed antenna arrays can be advantageous with their beam-and null-steering capabilities, however, testing them in the field is resource-intensive and non-repeatable. Therefore, evaluating them in virtual electromagnetic environments is reasonable prior to scheduling field-operational tests. Thereby the challenge arises that the angles-of-arrival of satellite signals deviate from those of their corresponding antennas due to the fixed orbital rotation of satellites and mechanical limitations of physical antenna placements. This discrepancy creates an unrealistic satellite constellation, eventually affecting directions-of-arrival estimation of incident signals which is crucial for interferer suppression. A Matlab tool was implemented to locate satellites near desired transmitter positions and numerically alter their orbital parameters to minimize their angular deviation from respective transmitters. Employing the tool, a realistic virtual satellite constellation with less than 1 degree deviation was emulated and experimentally verified for the test facility.
https://doi.org/10.23919/EuCAP57121.2023.10133419
Exposure change at two mobile radio base stations due to upgrading with 5G. - In: 17th European Conference on Antennas and Propagation (EuCAP 2023), (2023), insges. 5 S.
Radio frequency exposure measurements in the surroundings of two mobile radio base stations were performed before and after their upgrade to 5G to investigate exposure changes. The measurements were carried out in an urban environment in Berlin, and a 5G Dynamic Spectrum Sharing (DSS) base station and a 5G massive MIMO base station were investigated. At the first base station, a previous UMTS system was replaced by a DSS system (LTE and 5G share common resources) with unchanged total transmission power. The maximum possible exposure at five out of six measurement points remains unchanged within the measurement uncertainty. At the second base station under investigation, a 5G massive MIMO antenna technology was additionally installed to an existing mobile radio system. Here, maximum possible exposure increases of 6 to 11 dB occur at the investigated measurement points. A parallel recording of the 5G instantaneous exposure at the massive MIMO station shows that the exposure without provoking traffic load (signalization only) and at low traffic load exploits only 5-10% of the maximum exposure in terms of field strength.
https://doi.org/10.23919/EuCAP57121.2023.10133212
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
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
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