低信噪比下数字调制信号脉内特征提取

Identification of Digital Modulation Types Using Wavelet Transform at Low SNR

为了改善小波变换法在低信噪比下提取数字调制信号脉内特征时的性能,首先利用WVD变换在零频处既可以保持原始信号调制特性不变,又具有很好的噪声抑制作用的特性,对信号进行降噪处理,然后从理论上分析了PSK信号和FSK信号小波脊线的性质,根据不同调制信号小波脊线的差异可以得出其调制类型,进而可以得到信号的频率和码速等脉内调制信息。通过对低信噪比下PSK信号和FSK信号的计算机仿真,取得了较好的效果,也验证了方法的可行性。

A modified method for identifying the modulation type of digital signals is proposed to improve the performance of the wavelet transform method at low signal - to - noise ration. Using the Wigner - Ville distribution （WVD）, the additive noise embedded in the signal can be reduced, without modifying the modulation characteristics. And then the wavelet ridges of PSK signal and FSK signal are extracted in order to gain the in - pulse characteristics of these signals. The simulation results confirm that the method is effective and reliable.