适合高阶QAM的载波恢复算法

为解决DVB—C系统中多电平调制信号(如64，128，256QAM)的频偏捕获，描述了一种极性判决鉴相的算法，该算法可捕获高阶QAM信号的频偏达200kHz。对于一般的频偏较小的QAM信号可用传统的DD算法纠正。这样对收到的带有较大频偏和噪声、部分多径的基带信号就可先用极性判决捕获大频偏，稳定之后再用全星座判决纠正剩下的小频偏。

A carrier recovery algorithm for high order QAM

In this paper, a polarity decision and phase detection algorithm is presented, which is useful for carrier acquisition in high order QAM, such as 64QAM, 128QAM and 256QAM, in order to acquire the frequency offset in DVB-C system. The proposed carrier recovery algorithm can acquire frequency offset of high order QAM signals up to 200 kHz, The conventional DD algorithm can acquire small frequency offset. When receiving a baseband signal with large frequency offset,big noise and part multipath, a large frequency offset can be acquired by using polarity decision algorithm firstly. Finally when stabilized, the remaing small frequency offset can be acquiredwith full constellation decision.