Fast acquisition algorithm for high sensitivity, large frequency offset spread spectrum signals in inter-satellite communication systems

Abstract

Aiming at the complex environment of inter-satellite links for micro satellites, characterized by extremely low signal-to noise ratios, large Doppler frequency shifts, and data bit transitions, this paper proposes an improved acquisition algorithm that integrates semi-bit differential coherence and an efficient parallel architecture. The core of the algorithm lies in utilizing semi-bit differential coherent processing to fundamentally eliminate the limitations of data bit transitions on coherent integration, enabling millisecond-level long coherent integration to achieve high processing gain while avoiding the squaring loss associated with non-coherent accumulation. By introducing multi-channel parallel frequency search and a time-division multiplexing correlator architecture, the algorithm significantly reduces hardware resource consumption while ensuring high sensitivity and the ability to handle large frequency offsets. Theoretical analysis derives the processing gain, the mechanism for avoiding squaring loss, and the frequency offset tolerance of the algorithm. MATLAB simulations and FPGA practical tests demonstrate that this new algorithm can capture weak satellite signals, improve receiver sensitivity, and provide a high-performance solution for space borne terminals.