A new FFT acquisition scheme based on partial matched filter in GNSS receivers for harsh environments

FFT acquisition scheme based on partial matched filter is an important search method in GNSS receivers, which can scan the code phase and Doppler frequency by parallel search scheme. However, the detection probability reduces due to the coherent combing loss and scalloping loss. To solve this problem, we propose a new FFT acquisition method based on Partial Matched Filter (PMF-FFT) in GNSS receiver, in which, the IF signal is divided and central frequency is shifted before the matched filters, and the FFT results are combined to search the Doppler frequency. The performance of the scheme is analyzed by amplitude response of the system. Both analysis and simulation results show that the new scheme has a larger acquisition range without adding the FFT points, which is quite appropriate for dynamic and weak signal environments. We also do a comparison based on the collected data test, showing that the PMF-FFT scheme outperforms the other three methods generally used in the GNSS receivers. Moreover, we apply an FPGA&DSP hardware receiver to verify the practicability and superiority of our method, which turns out our method can extremely reduce the acquisition time in a cold start condition, compared to the serial scheme.