OFDM系统中一种改进的全数字定时跟踪环

将全数字锁相环应用到OFDM系统的定时跟踪中时,有两个重要的问题需要解决,即误差信号归一化的问题和锁相环在多径衰落信道条件下容易失锁的问题.针对这两个问题,提出了合适的解决方案.即通过采用一个中间分支来解决误差信号归一化的问题,通过多径搜索来解决锁相环容易失锁的问题.研究结果表明,建议的解决方案可以真正有效地解决OFDM系统中的定时跟踪问题,并使锁相环在多径衰落信道条件下仍能正常工作.

Improved all digital timing tracking loop in OFDM systems

When all digital phase-locked loop(PLL) is applied in OFDM systems,two problems must be solved.The first is how to normalize the error signal,and the second is how to avoid the phenomenon of out-of-lock in multipath fading channel.The two problems were analysed and a suitable solution scheme was presented.Namely the middle branch was used to solve the first problem,and the way of searching multipath was used to solve the second problem.The results show that the proposed scheme can effectively solve the problem of timing tracking for OFDM systems and make phase-locked loop work normally in multipath fading channels.