低轨星DSSS信号快速捕获技术研究

Research on Fast Acquisition Technique for DSSS Signal in LEO Satellite

本文介绍了一种基于非相干的低轨星直接扩频信号快速捕获技术。低轨星高速运动所带来的大多普勒频偏成为制约传统捕获方法的主要因素,导致捕获性能严重恶化,同时低轨星快速的过境时间要求加快信号捕获速度。部分匹配滤波器可在时域快速完成码相位搜索,快速傅里叶变换可在频域完成多普勒频移搜索。相比传统捕获方法,部分匹配滤波器结合快速傅里叶变换的捕获方法可快速完成大范围多普勒频偏搜索,为低轨卫星直扩导航信号的接收提供支撑。

This paper describes a non-coherent technique for fast acquisition of direct sequence spread spectrum(DSSS)signals transmitted by low earth orbit(LEO)satellites.Large Doppler offsets brought by the high speed moving LEO have become the main obstacle of the traditional acquisition methods,resulting in seriously worsen performance of acquisition.The shorter lasting time demands faster acquisition speed.This paper discusses the use of a set of partial matching filters for code phase searching in time domain,combined with a fast Fourier transform(FFT)for the purpose of parallel Doppler estimation.Compared to conventional techniques,faster code phase searching speed and a wider range of Doppler offsets can be acquired in less time.This can afford the bases for the research on DSSS signals acquisition of LEO satellites.