摘要
针对高阶QAM系统对于符号定时、载波恢复精度的严格要求,文章提出了一种全数字的同步方案。首先,利用非相干载波解调,提取符号定时信息。然后,利用已获取的定时信号进行载波相位跟踪,最终得到与相位真实值关于模π/2同余的估值。对于包含差分编、译码的QAM系统,上述方法不需要专门设计同步头即可为正确解调提供稳定可靠的同步信息,非常适宜数字实现。
To satisfy the stringent requirements of symbol timing and carrier phase recovery for a QAM system with large constellation, this paper presents an all digital synchronization scheme. Symbol timing is implemented prior to carrier recovery. Following the achieved symbol synchronization output, carrier phase acquisition can be performed. The ultimate phase estimation is equivalent to its true value as far as module π/2 is concerned. For a QAM system embracing differential coding procedure, the proposed approach is capable of supplying stable and optimal synchronization information for subsequent demodulation without specially designed pilot signal.
出处
《计算机与网络》
1999年第12期18-20,共2页
Computer & Network
关键词
QAM
符号定时
载波恢复
眼图
最大似然估计
QAM Symbol timing Carrier synchro-nization Eye pattern ML estimation
