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

Based on the theory of instantaneous frequency measurement, a method of demodulation for PCM/FM signal with Doppler frequency offset is presened. Firstly, through estimating Doppler frequency offset by instantaneous frequency measurement, the method corrects the frequency offset of PCM/FM signal and improves the precision of bit synchronization. Then, according to the relation between two adjacent points of bit synchronization, it realizes demodulation. The paper discusses the basic principle and the implementation of the method, analyses some factors that can affect the precision of instantaneous frequency measurement and the effect of Doppler frequency offset on demodulation, and proposes methods 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.