Improved FFT-based algorithm for GPS signal acquisition

摘要

This paper describes a GPS signal acquisition method using FIR decimation filter and FFT. First, FIR decimation filter was used to decimate the digital IF signal after the carrier wipe-off. Then, the C/A code phase and carrier frequency was determined through the processing of FFT-based acquisition method. Finally, the Gaussian noise was added to the digital IF signal to analyze the performance of noise immunity. The model of system simulation was provided and the performances of this method compared with conventional FFT-based acquisition and averaging correlation method was analyzed. The simulation results show that acquisition with FIR decimation filter, compared with FFT-based acquisition without decimation, can reduce computational complexity and speed up the signal acquisition processing, while the max correlation value descends about 10%. Compared with averaging correlation acquisition method, the max correlation value between the received signal and the local C/A code can be improved by an average of 30%. Moreover, this acquisition method has a better performance of noise immunity than other two methods.