基于小波变换的MDPSK信号盲解调算法

Blind demodulation algorithm for MDPSK signals based on wavelet transforms

在M进制差分相移键控(M-ary differential phase-shift keying,MDPSK)信号解调中,非合作信号的载频估计误差或者高动态环境引起的Doppler频移都会使得解调性能恶化,甚至无法解调。针对这个问题提出了一种盲解调算法,该算法基于MDPSK信号相位跳变点频谱分布与相位跳变量之间的对应关系,利用小波变换的滤波特性提取MDPSK的频谱分布特征来完成信号解调。该算法不需要载波恢复,并且对载频估计误差也不敏感。仿真结果表明:当BDPSK信号Es/n0为5 dB时,QDPSK信号Es/n0为10 dB时,盲解调性能比理论值恶化约为2 dB;并且当载频估计相对误差小于15%时,解调性能无明显下降。

The demodulatinn of MDPSK （M-ary differential phase-shift keying） signals can be badly degraded, and is sometimes not even achievable due to carrier frequency estimation errors in the non-cooperation signal or the Doppler shift in dynamic environments. A blind demodulation algorithm was developed based on wavelet transforms to extract the spectrum features identified from the phase magnitude. The method requires no carrier recovery and has low sensitivity to the carrier frequency estimation error. Simulations demonstrate that the demodulation performance is about 2 dB lower than the theoretical lower bound at Es/no = 5 dB for BDPSK signals and at Es/no = 10 dB for QDPSK signals. The demodulation performance is not significantly degraded for carrier frequency estimation errors lesser than 15 %.