一种扩展载波环频率捕获范围的方法

在MPSK数字载波恢复中,可以通过锁频锁相环捕获大范围频率偏移。低信噪比下,锁相环的频率捕获范围较小,而工程中锁频环剩余频偏通常较大,因而需要扩展锁相环的频率捕获范围。描述了频差估计以及COSTAS环中相位检测技术的实现方法,分析了COSTAS环的相位检测特性,并根据这种算法的鉴相特性提出了一种扩展频率捕获范围的载波恢复方法。以QPSK为例,通过MATLAB仿真了这种技术在低信噪比情况下对频率偏移的检测与跟踪性能,仿真结果表明,提出的方法适合低信噪比下大范围的频率捕获。

A Method to Expand the Acquisition Range of Carrier Recovery Loop

In digital MPSK carrier recovery, the frequency offset can be captured by frequency and phase lock loop. At low SNR, PLL has a very narrow frequency capture range, and frequency lock loop has larger frequency offset remained in engineering implementation. So the PLL＇s capture range needs expanding. In the paper, the implementation of frequency offset estimation and COSTAS loop phase detector is described, and the phase detector characteristics are analyzed. A technique for expanding the frequency capture range is proposed on the base of the analysis. Taking QPSK for example, a MATLAB simulation is performed for the detection and tracking performance of this technique. The result indicates that the carrier recovery technique is suitable for large-scale frequency offset capture at low SNR.