Enhancing GNSS Resilience: An Adaptive Look-Up Table Approach for Analog Null Steering

Ali Massoud, Haidy Elghamrawy, Mai Hassan, Aboelmagd Noureldin

Peer Reviewed

Abstract:	Null steering is a vital technique for mitigating jamming attacks in antenna arrays, such as those used in global navigation satellite system (GNSS) receivers, by placing nulls in the radiation pattern to suppress interference and enhance the Signal-toInterference Ratio (SIR). In this work, analog null steering is utilized as it eliminates the need for high-sampling-rate analog to digital converters (ADCs), making it a more cost-effective and power-efficient alternative to digital null steering. Additionally, it offers greater robustness against array calibration errors, enhancing overall system reliability. To leverage these advantages, efficient algorithms are required to determine and apply the optimal nulling weights in real-time. One approach to analog null steering is the power inversion (PI) method, which precomputes nulling weights for all possible directions on a PC and embeds them into the antenna array's firmware. In existing methodologies, during a real jamming scenario, these weights stored in a look-up table (LUT) are sequentially searched to find those that minimize the received power, which are then applied to the antenna elements. The weights are implemented using amplitude control via attenuators and phase control via phase shifters. While conventional PI methods typically use fixed directional resolution for null steering, they face a trade-off between search speed and nulling performance. Coarse-resolution LUTs enable fast searches but result in shallow nulls, limiting their ability to suppress high-power jammers. Conversely, fine-resolution LUTs provide deeper nulls to mitigate strong interference effectively but increase search time and memory usage. This paper presents an adaptive LUT method selects a subset of fine-resolution entries based on jammer power, reducing search time and LUT size while maintaining deep nulls. Using a 4-element Uniform Circular Array, performance is evaluated against fixed-resolution LUTs. Metrics include spatial coverage at target null depth and LUT size, which determines search time needed for GNSS jamming mitigation.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	2173 - 2182
Cite this article:	Massoud, Ali, Elghamrawy, Haidy, Hassan, Mai, Noureldin, Aboelmagd, "Enhancing GNSS Resilience: An Adaptive Look-Up Table Approach for Analog Null Steering," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 2173-2182. https://doi.org/10.33012/2025.20284
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