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在高动态通信系统中,由于载体的相对运动,使载波附加了较大的多普勒频移。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。文中讨论了该方法部分相关器长度和FFT点数对捕获性能的影响,推导相关损失与最大多普勒频移和相关器长度的关系,为分析捕获系统的捕获范围和选取相关器参数提供依据,给出两种确定分段相关器长度X的方法。最后仿真证明在PN捕获的同时该方法能够准确估计多普勒频移。
In high dynamic communication systems, the carrier is given a larger Doppler shift due to the relative motion of the carrier. Using a set of partial correlators combined with Fast Fourier Transform for pseudo-code capture, the two-dimensional search of code phase-Doppler frequency can be reduced to one-dimensional search, greatly reducing acquisition time. In this paper, we discuss the influence of partial correlator length and FFT point on the acquisition performance, deduce the relationship between the correlation loss and the maximum Doppler shift and the correlator length, provide the basis for analyzing the acquisition range of the acquisition system and choosing the correlator parameters, Two methods are given to determine the segment correlator length, X. The final simulation proves that this method can accurately estimate the Doppler shift while PN capturing.