卫星移动通信中利用Chirp信号的时频同步算法

Timing and Frequency Synchronization Algorithm Based on Chirp Signal in Mobile Satellite Communication System

卫星移动通信中信号受到多普勒效应和阴影衰落效应的影响,导致信号变化快且很微弱,对系统接收性能影响很大。提出一种用于卫星移动通信终端下行链路时频同步新算法。根据本地扫频信号与接收Chirp信号相关后峰值频率变化规律来进行定时捕获,同时实现了频偏估计。通过仿真和分析,给出了不同信噪比环境下,利用Chirp信号进行定时捕获和频偏估计的性能。结果表明,在阴影衰落导致的信噪比很低和高速移动导致的多普勒频偏的情况下,定时捕获性能优越,频偏估计性能很好地满足系统要求。

Influenced by the Doppler frequency drift and shadow fading, signals in mobile satellite communication system attenuate and deteriorate a lot, affecting the general receive performance of the system. A novel timing and frequency synchronization ＇algo- rithm in mobile satellite communication system is proposed. The new algorithm is suggested to capture the Chirp signal on the down- link at the receiving terminal. According to the frequency feature of chirp signal multiplied by a local reference signal, the proposed algorithm provides a way to capture chirp signal and estimate the frequency offset. Through simulations and analysis, the perform- ance of acquisition of Chirp signal and frequency offset estimation are evaluated under different SNRs. The results show that under the circumstance of low SNR caused by shadow fading and Doppler frequency drift in high-speed environment, the proposed algo- rithm achieves superior acquisition performance, and frequency offset estimation performance satisfy the system requirement.