Adaptive Anti-Jamming Acquisition of BOC Signal in Beidou Satellite Navigation Receiver

Binary offset carrier (BOC) modulation is widely utilized in the modern BeiDou Satellite Navigation System (BDS) to facilitate spectrum sharing and enhance communication quality. However, acquisition performance is hindered by inherent ambiguities and jamming, making robust receivers essential. This paper analyzes a specific chirp-type jammer model and proposes an acquisition algorithm that combines adaptive subspace projection (ASP) with a partial matched filter-fast Fourier transform (PMF-FFT) scheme, enhanced by high-order polynomial least squares (HOPLS) optimization. The optimal subspace length is determined using the maximum correlation-based signal-plus-noise-to-jamming ratio (CSNJR) method. To ensure efficient jamming mitigation and minimize correlation loss in the PMF stage-both of which benefit from a shorter analysis length-the two processes are seamlessly integrated to streamline the overall system. The received signal is projected onto an orthogonal subspace, mixed with the local carrier, and processed using the PMF-FFT algorithm for coarse and unambiguous acquisition. To address the trade-off between reduced PMF length and increased FFT complexity, HOPLS curve fitting is employed to optimize Doppler frequency offset (DFO) acquisition accuracy while maintaining computational efficiency. Performance is evaluated under varying jamming-to-signal ratios (JSR) and instantaneous frequency (IF) estimation errors, with PMF length and FFT points analyzed for their effects on acquisition. Simulation results demonstrate that the proposed method effectively suppresses jamming, maintaining residual jamming power below the received satellite signal power of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-130 \rm{dBm}$</tex-math></inline-formula> across a JSR range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0--60 \rm{dB}$</tex-math></inline-formula>, and achieves better performance in detection probability over conventional techniques. The mean square error (MSE) of DFO estimation is reduced by approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10 \rm{dB}$</tex-math></inline-formula>, approaching the Cramér-Rao lower bound (CRLB). Moreover, the average acquisition time (AAT) is average 3.8 seconds shorter than that of time-domain (TD) acquisition algorithms. The HOPLS scheme allows the FFT size to be fixed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{12}$</tex-math></inline-formula>, ensuring low computational complexity. The proposed ASP-based acquisition framework thus provides a robust and efficient solution for satellite signal acquisition under severe jamming conditions in BDS.