Iterative Greedy Look-Up Table Optimization for Fast Analog Null Steering in GNSS Anti-Jamming Receivers

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Abstract
Global Navigation Satellite Systems (GNSS) are increasingly vulnerable to intentional jamming, making efficient interference mitigation essential for robust navigation. Analog null steering provides a low-complexity anti-jamming solution by steering radiation pattern nulls toward interference without requiring high-speed ADCs at each antenna element. Conventional Power Inversion methods rely on pre-computed Look-Up Tables (LUTs) storing nulling weights for all jammer directions, but face a critical trade-off: coarse-resolution LUTs enable rapid searches with shallow nulls and incomplete coverage, while fine-resolution LUTs achieve deeper nulls at prohibitive computational cost and latency. This paper introduces an adaptive LUT optimization framework based on Iterative Greedy Optimization (IGO) that dynamically adjusts the search space according to measured jammer power. Unlike population-based methods such as genetic algorithms and simulated annealing, IGO exploits the submodular structure of the null coverage problem to achieve deterministic convergence with guaranteed spatial coverage in a single forward pass. IGO incrementally selects only the most effective entries from a fine-resolution baseline, minimizing null overlap while guaranteeing complete spatial coverage at required suppression depths. Simulations with a four-element Uniform Circular Array demonstrate predictable LUT scaling with target null depth and search-time reductions up to 20× compared with exhaustive search. Experimental validation using a Calian Controlled Reception Pattern Antenna (CRPA) confirms that IGO-optimized LUTs meet or exceed target suppression levels while reducing search space by up to 96.5%. Hardware-in-the-loop navigation testing with a Syntony GNSS simulator under severe jamming (J/S = 65 dB) demonstrates that IGO maintains full positioning availability while preventing complete outages experienced by unprotected receivers. Navigation analysis reveals IGO achieves twice faster average recovery following jammer onset compared to exhaustive search (3.56 s vs. 7.11 s), while delivering equivalent carrier-to-noise ratio and satellite tracking. These results establish the proposed approach as a highly effective and near-optimal solution for resource-constrained GNSS receivers.
Funding Information
  • Alliance grant from the Natural Sciences and Engineering Research Council of Canada (ALLRP 601784 - 24)
  • Canada Research Chair Program (CRC-2023-00319)

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