一种数字集群系统中GMSK信号的相偏跟踪算法

A phase offset tracking algorithm for GMSK signal in digital trunking system

针对国内某集群系统采用准相干解调时遇到的频率同步问题,进行研究讨论并提出解决方案。由于准相干解调对系统收发的频率同步精度要求非常高,采用常规的频偏估计补偿思路难以满足要求,从而使得准相干解调的性能优势无法体现。针对此问题,提出了一种分段相位跟踪算法:通过对频偏补偿后残留频偏引起的大相位误差进行分段相位跟踪并补偿的方式,来降低残留频偏对系统解调性能的影响,所得解调性能与理想频率同步下的性能基本一致。所提算法尤其适用于频偏估计误差较大的系统。

In this paper,the frequency synchronization problem encountered by a domestic trunking system using quasi-coherent demodulation is studied and discussed,and the solution is proposed.Because quasi-coherent demodulation requires very high frequency synchronization accuracy of transceiver systems,it is difficult to meet the requirements by using conventional frequency offset estimation and compensation scheme,which makes the performance advantages of quasi-coherent demodulation unable to be reflected.In order to solve this problem,this paper proposes a segmented phase tracking algorithm.By tracking and compensating the large phase error caused by residual frequency offset after frequency offset compensation,the influence of residual frequency offset on the demodulation performance of the system is reduced,and the obtained demodulation performance is basically consistent with the performance under ideal frequency synchronization.The algorithm proposed in this paper is especially suitable for systems with large frequency offset estimation errors.