基于PMF-FFT的多普勒频偏估计与跟踪算法

Doppler Frequency Offset Estimation and Trackingalgorithm Based on PMF-FFT

为降低高动态环境下卫星通信系统中信号的捕获与跟踪时间,文章提出了一种多普勒快速捕获与跟踪方法。在信号捕获阶段通过高倍采样率下进行匹配FFT进行快速捕获,大大提高了捕获带宽且捕获时间控制在两个帧周期以内;在多普勒跟踪阶段,通过捕获算法计算频偏值并进行补偿,再采用锁频环(FLL)辅助锁相环(PLL)进行多普勒的跟踪,频偏值的补偿缩短了FLL的入锁时间,从而提高了多普勒的跟踪速度。仿真和工程实践结果表明,该算法实现了在频偏范围为4倍符号速率,频偏变化率在2倍导频速率下的多普勒快速捕获与跟踪。

In order to reduce the signal acquisition and tracking time in LEO satellite communica-tion systcm,a Doppler fast acquisition and tracking method is proposed in this paper.In the sig-nal acquisition stage,matching FFT is used for fast acquisition at high sampling ratc,which greatly improves the acquisition bandwidth and the acquisition time is controlled within two frame periods,In the Doppler tracking stage,the frequency offset value is calculated and com-pensated by the acquisition algorithm,and then the frequency locked loop(FLL)is used to assist the phase locked loop(PLL)to track the Doppler.The compensation of the frequcncy offset value shortens the locking time of FLL,thereby improving the Doppler tracking speed.Simula-tion and engineering practice results show that the algorithm can achieve Doppler fast acquisition and tracking under the frequency offset range of 4 times the symbol rate and the frequency off-set change rate of 2 times the pilot rate.