A new array concept using spatially distributed subarrays for unambiguous GNSS interference mitigation in automotive applications

Abstract

Radio frequency interference (RFI) poses a severe problem for conventional GNSS receivers. Even low powered RFI can block the reception of satellite signals and prevent a position determination. Antenna array systems have been proven suitable to counteract RFI by incorporating spatial processing techniques. The large size of uniform rectangular arrays (URA) with half‐wave antenna spacing impedes an installation in cars intended for the consumer mass market, where a hidden installation is a strict requirement by industry and customers. This paper introduces a new approach, where a conventional URA is split into distributed linear subarrays with the aim to reduce their footprint but to maintain the possibility of spatial processing. The achievable gain in robustness against RFI is evaluated. Drawbacks in terms of manifold ambiguities and their consequences for spatial processing techniques are also discussed. Furthermore, the accuracy of positioning results derived from a field test is put into context with a single antenna receiver.

Space-Time Adaptive Processing as a Solution for Mitigating Interference Using Spatially-Distributed Antenna Arrays

“…As a countermeasure against interference and to amplify the weak GNSS signals received, we used a state-of-the-art blind two-stage beamforming technique (Kurz et al, 2012) as depicted in Figure 5. We analyzed the performance of this technique in several previous publications (Brachvogel et al, 2018(Brachvogel et al, , 2020a(Brachvogel et al, , 2020b in the context of narrowband jamming scenarios using GPS L1 C/A signals. This technique detects incident signals without the need for further information by estimating their correlation before and after PRN despreading.…”

“…In this paper, we introduce adaptations to the interference mitigation stage. The post-correlation beamforming algorithm combines the satellite signals using a similar approach, which is briefly explained in (Brachvogel et al, 2020b;Kurz et al, 2012). For the sake of clarity, this is not explained further in this paper.…”

“…However, the new array design does come with some drawbacks. From the signal processing perspective, the increased size of the lever arm between the ULAs and the antenna elements may lead to differential effects on the antenna signals (Brachvogel et al, 2020b), including, for example, differential non-negligible delays in the received baseband signal, deviating Doppler frequencies with respect to the carrier signal, or unequal power levels due to hardware imperfections and shading from the metallic car body that blocks the signals to be received from the individual antenna elements. This implies that the correlation of an incident signal received at the spatially distributed antenna elements may be reduced in this array design compared to the conventional URA in which the spatial proximity guarantees a strong correlation.…”

“…We have studied the impact of these effects in experimental simulations using a specific range of bandwidths and global positioning system (GPS) L1 C/A signals (Brachvogel et al, 2020b). For signals with higher bandwidths, for example, those used in GPS L5 or GALILEO E5a, decorrelation via differential delay is expected to be a dominant factor.…”

LO and Calibration Signal Distribution in a Multi-Antenna Satellite Navigation Receiver

“…Therefore, our goal was to realize a more compact GNSS receiver system. We proposed to split the full number of four antenna elements into two distributed two-element subarrays [12]. This approach effectively increases the number of possible mounting spaces by enabling the installation of sub-arrays in distant parts of a car, such as side mirrors or other suitable car body appliances.…”