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在大多普勒频移环境下,使用一组部分相关器结合快速傅里叶变换进行伪码捕获,可以将码相位-多普勒频率的二维搜索降为一维搜索,大大减少了捕获时间。基于部分匹配滤波器(PMF,Partial Matched Filter)-快速傅里叶变换(FFT,Fast Fourier Transform)的PN码捕获中,部分相关器的相关运算会使滤波器的频幅响应产生衰减。这里推导了相关损失与相关器长度和多普勒频移的关系,为分析捕获系统的捕获范围和选取相关器长度提供理论依据,同时给出选取分段相关器长度X值的方法。仿真表明给出的选取X值的方法是可行的。
In a large Doppler shift environment, a set of partial correlators combined with fast Fourier transform is used for pseudo-code capture to reduce the two-dimensional search of code phase-Doppler frequency to one-dimensional search, greatly reducing the capture time . Partial Correlation Filter (PMF) -Fast Fourier Transform (PNF) PN code acquisition, part of the correlator correlation operation will make the filter frequency response attenuation. The relationship between loss and correlator length and Doppler shift is deduced here, and provides a theoretical basis for analyzing the capture range and the length of correlator. At the same time, the method of choosing the length X of the correlator is given. The simulation shows that the method of choosing the value of X is feasible.