关键词: 中短波信道, 数字AM广播, 时间同步, 正交频分复用

Abstract: OFDM is an effective modulation technique for high-rate and high-speed transmission over the frequency selective fading channel.However, the OFDM system can be extremely sensitive and vulnerable to timing synchronization errors.In this paper, a low-complexity two-stage timing recovery scheme is proposed. The timing recovery process can be divided into symbol synchronization and sample clock synchronization.In the former process, an improved ML algorithm is proposed.Its performance can approach the optimal ML algorithm without estimating SNR and therefore can have lower complexity.In the latter process, an simple synchronization algorithm is proposed using scatter pilots to estimate sample clock phase errors, and a low pass loo p filter is used to track the symbol timing drift caused by sample clock frequency offset.Simulations are carried out on DAMB channels, and the results indicate that our proposed scheme can achieved good performance and are robust to multipath fading channels.Its low complexity enables the scheme to operate easily run on the DSP chip.

Key words: DAMB channel, OFDM, timing recovery, digital AM broadcasting