短波突发FSK信号解调技术研究

Research of demodulation on HF burst FSK signal

针对短波突发FSK信号解调中存在突发检测和同步判决的问题,提出了一种基于谱熵检测和短时傅里叶变换(Discrete short time Fourier transform,DSTFT)判决的突发信号解调方法。根据信号和噪声在频段内功率谱熵分布的不同,利用谱熵可有效区分信号段和噪声段,为信号解调提供连续有用信息。在FSK解调中提出了具有抗噪声性能的载频附近功率累积量的码元判决方法,同时采用具有抗频偏的载频附近峰值比的码元同步方法。仿真结果表明:基于谱熵的检测方法可有效满足突发信号检测,本文解调方法在低信噪比下具有更低的解调误码率,结合谱熵检测可有效满足突发信号的精确识别和解调。

Aiming at the problem of burst detection and synchronization judgment on FSK signal demodulation,a method of burst signal demodulation based on spectrum entropy and discrete short time Fourier transform(DSTFT) is proposed. According to power spectrum entropy of signal and noise is different in frequency band,the method of spectrum entropy can distinguish signal segment and noise segment. Then the symbol decision method based on power accumulation for the region near the carrier frequency which has good anti-noise performance and the symbol synchronization method based on the peak ratio near the two carrier frequency which is resistant to carrier frequency offset is used. The simulation results show that the method of spectrum entropy can detect burst signal effectively,and the demodulation method has lower BER under low signal-to-noise conditions. The method based on spectrum entropy and DSTFT can demodulate burst FSK signal efficiently.