基于瞬时测频的PCM/FM信号解调方法研究

Research on Method of Demodulation for PCM/FM Signal Based on Instantaneous Frequency Measurement

根据瞬时测频理论,提出了一种新的PCM/FM遥测信号解调方法。首先通过瞬时测频方法,估计信号中的多普勒频移,不但修正了信号中存在的多普勒频偏,而且提高了码同步的精度。然后根据PCM/FM信号相邻码同步点间的对应关系,实现了信号的解调。详细介绍了此种解调方法的基本原理及实现过程,分析了影响瞬时测频精度的因素以及多普勒频率对解调性能的影响,提出了提高瞬时测频精度和解调性能的方法。计算机仿真结果表明,该方法解调性能优越,抗干扰能力强,便于软件编程及DSP器件实现,具有一定的应用价值。

Based on the theory of instantaneous frequency measurement, a method of software demodulation for PCM/FM signal with Doppler frequency offset is presented. Firstly, through estimating Doppler frequency by instantaneous frequency measurement, the method not only corrected the frequency offset of PCM/FM signal, but also improved the precision of bit synchronization. Then, according to the relation between two closed points of bit synchronization, the demodulation was realized. The basic theory and the course about the method were discussed. Some factors were analyzed that could affect the precision of instantaneous frequency measurement and the effect of Doppler frequency offset on demodulation. Themethods were proposed to improve the precision of instantaneous frequency measurement and the performance of demodulation. The results of computer simulation show that the method with a bright future for application is good at anti-jamming, better than other methods of demodulation and convenient to be realized by software and DSP.