Modeling and simulation of FM detection by zero-crossing in the presence of noise and DS interference

A signal model for a direct sequence (DS) system and an FM system is presented, then FM signal demodulation in the presence of interfering DS and noise is simulated. The FM receiver used utilizes a zero-crossing (ZX) scheme for demodulation. To demonstrate the ZX detection of an FM signal, two algorithms are developed and simulated. The results show that for the cases considered, the FM systems could reasonably coexist with the DS spread spectrum systems. Furthermore, ZX demodulation schemes are shown to be useful with microprocessor based detection systems.