一种面向深空测距的大多普勒频偏信号捕获算法

An Acquisition Algorithm of Signal with Large Doppler Shift in Deep Space Pseudocode Ranging

在深空测距任务中,高精度的伪码捕获是后续执行伪码跟踪的关键前提。传统基于时频二维搜索的频偏估计算法对于深空测距中频率偏移范围较大的情况难以满足伪码捕获实时性要求。为此,提出了改进的时频二维搜索算法,通过在传统时频二维搜索算法的前端引入快速傅里叶变换(Fast Fourier Transform,FFT)算法对多普勒频偏进行预估,避免在大多普勒范围的频点遍历,能够有效降低频偏估计的时间开销。实验表明,该方法能够在大多普勒频偏环境下利用有限的硬件资源快速地实现伪码捕获,满足伪码捕获的实时性要求。

In deep space ranging tasks,high-precision pseudocode acquisition is the key premise for subsequent pseudo-noise(PN)code tracking.For deep space ranging in which the Doppler shift is large,it is difficult for traditional Doppler shift estimation algorithm based on the time-frequency two-dimensional(2D)search to meet the real-time requirements of PN code capture.Therefore,an improved time-frequency 2D search algorithm is proposed.By introducing the fast Fourier transform(FFT)algorithm at the front end of the traditional time-frequency 2D search algorithm to predict the Doppler shift,traversing the frequency points in the huge Doppler shift is avoided,thus effectively reducing the time cost of frequency offset estimation.Experiments show that this method can quickly achieve PN code capture with limited hardware resources in huge Doppler shift environments,and meets the real-time requirements of PN code acquisition.