Improved SFFT algorithm for weak signal acquisition in BeiDou satellite navigation

Satellite signal acquisition is a critical component for BeiDou receivers to achieve PNT functionality, with its performance directly determining system availability in complex environments. Traditional time-frequency two-dimensional parallel search methods face two major bottlenecks: computational complexity increases dramatically when processing high-dynamic Doppler shifts, and under weak signal conditions, they struggle to meet high-sensitivity, low-power requirements due to the squaring loss effect and elevated noise floor. To address these challenges, this paper proposes an innovative acquisition architecture. 1) Combining an equivalent frequency compensation cyclic shift search mechanism with sparse Fourier transform (SFT), eliminating traditional two-dimensional traversal, and transforming Doppler search into cyclic shifts to reconstruct frequency search logic. 2) Introducing SFT to efficiently utilize the frequency-domain sparsity of BeiDou signals, computing only significant frequency components to optimize frequency-domain correlation efficiency. 3) Designing an improved differential coherent integration algorithm. For weak signal acquisition, differential coherent technology is applied by constructing a phase difference model between adjacent symbol periods, effectively canceling data bit transition effects and significantly suppressing noise floor elevation, achieving an SNR gain improvement of approximately 3 dB. Compared to conventional methods, under the same hardware conditions, the proposed solution reduces computational complexity by 62 % and improves acquisition sensitivity by 4 dB. For weak signals at -45 dBm, the acquisition success rate reaches 95 %. The novel “Doppler cyclic shift search-SFT” fusion architecture and differential coherent technology provide a new technical approach for efficient, high-sensitivity BeiDou signal acquisition, demonstrating significant theoretical breakthroughs and broad engineering application prospects.