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

摘要： 提出一种基于FFT弱信号的中频信号块累加的差分相干累积算法。新算法利用中频信号块累加在中频信号FFT之前进行累加，减少相干运算量；利用差分相干累积在IFFT之后进行累积，消除平方损耗，解决了传统的基于FFT弱信号捕获时相干积分运算量过大和非相干累加算法引起的平方损耗问题。仿真实验表明该算法完成了对输入信噪比为－39 dB/2 MHz的信号的快速准确捕获，减少相干运算量，消除了平方损耗，提高了信噪比。

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