一种改进的直扩系统大频偏二次捕获算法

针对卫星通信中低信噪比大频偏信号的精确捕获问题,提出了一种改进的直扩系统二次捕获算法. 算法首先通过基于FFT的码相位并行搜索完成频偏的预估计和补偿,构造一个不含扩频码的准基带信号,然后对此信号采用含有辅助结构的FFT实现频率的精确估计和校正. 仿真结果表明,本文所提算法与传统二次捕获算法相比捕获性能大致相当,资源消耗降低24%,捕获时间减少84%. 给出了不同信噪比和扩频比下关键参数的选取方法,使算法具有较高的实用性. 

An Improved Double Acquisition Algorithm for DSSS System

An improved double acquisition algorithm for DSSS system with large Doppler frequency shift and low SNR was proposed. Firstly, the parallel search algorithm was utilized with code phase based on FFT for pre-acquisition and compensation of frequency shift. Secondly, after achieving the synchronization of the PN code and carrier, decreasing and demodulating the received DSSS signal wound be executed with the local synchronized code and carrier. Finally, accurate frequency estimation was achieved using FFT with assistant module. Simulation results show that the improved algorithm can reduce resource consumption by 24% and shorten acquisition time by 84%. With a relevant parameter selection method, the algorithm achieves better performance with various SNRs and spreading rates.