低轨卫星CDMA突发通信的信号检测与捕获分析以及基于FPGA的实现

Signal Detection and Acquisition in CDMA LEO Satellite Communication System with its FPGA Implementation

CDMA作为一种抗噪声强、带宽分配灵活，保密性强的传输接入方式被广泛的应用于民用、军用低轨卫星通信系统中，而信号的捕获和同步分析对于设计一个可实现的低轨卫星CDMA接收机是至关重要的，在低轨卫星信道上的CDMA传输必须着重考虑以下两点；低轨卫星信道上的衰落以及相对较大的多普勒频移。本文针对低轨卫星信道特征，着重分析了在此信道上的信号检测（Signal Detection),初始的码捕获（Code Acquisition)，载波捕获(Carrier Acquistion)方法以及性能，并给出了基于FPGA实现的方案。

CDMA technology is widely used in LEO satellites communication because of many merits offered by CDMA system such as suppression of ingress noise, flexibility of bandwidth assignment and the security. The key issue of the practical burst mode DS-CDMA-QPSK receiver is signal detection and acquisition. There are two key problems, fast fading and the large Doppler frequency offset, in satellite channel have to be considered. In this paper, emphasis is put on the schemes and the performance of the initial signal recognition, code acquisition and Doppler frequency acquisition based on the characteristics of satellite channel. The FPGA implementation of the proposed method is also provided.