利用改进相频检测器实现大频偏M-PSK信号的快速载波同步

Fast Carrier Synchronization of M-PSK Signals under Large Frequency Offset

卫星通信中,接收机经常要在较大频偏下实现对M-PSK信号的载波同步;频偏较大的条件下,使用锁相环对信号进行载波同步需要较长的捕获时间,而且如果频偏超出锁相环捕获范围,将无法实现捕获。基于传统的相频检测器,提出了一种改进方案,通过增加相频检测器的"保持"区间,增大了频偏较大时相频检测器输出的直流分量,从而可以更快地实现对频偏的捕获。仿真结果表明,该方案可以帮助锁相环实现更大的频偏捕获范围和更快的捕获速度。

In satellite communications, digital receivers often need to achieve cartier synchronization under large residual frequency offset. Under large frequency offsets, long acquisition time is needed when using phase-lock loop（PLL） for carrier synchronization, and acquisition will fail if frequency offset is beyond the acquisition range of PLL. Based on conventional phase-frequency detector （PFD）, an improved solution is proposed, which can aid PLLs to gain a wider acquisition range and fast acquisition speed. The main idea is to prolong the ＂hold＂ range for of PFD, so that a greater direct current （DC） will occur when frequency offset is large. The improved solution is verified by simulation results.