关键词: 全球定位系统（GPS）, 弱信号, 捕获, 中频信号块累加, 差分相干

Abstract: A differential coherent accumulated acquisition algorithm based on Fast Fourier Transform（FFT） weak signal block accumulation of the intermediate frequency is presented in this paper. To reduce coherence computation, the proposed algorithm performs the block accumulation of the intermediate frequency signal before FFT. To solve the two problems in traditional acquisition algorithms based on FFT weak signal, namely great computation of coherent integral and square loss caused by incoherent accumulation, the proposed algorithm performs the differential coherent accumulation after IFFT. The simulation experimental results show that the algorithm quickly and accurately acquires the input signal with SNR of －39 dB/2 MHz. The algorithm reduces the calculations, eliminates square loss and improves the signal to noise ratio.

Key words: Global Positioning System（GPS）, weak signal, acquisition, block accumulation of intermediate frequency, difference correlation