FM demodulation in the presence of multiplicative and additive noise

Abstract

A theory of noise in ideal frequency demodulators is developed for the case when the input carrier is a Gaussian process rather than having a constant amplitude. Exact expressions for the demodulator output are obtained which include the effects of additive Gaussian noise in the intermediate frequency stage. Numerical results are evaluated for the output spectrum and noise power following baseband filtering. A simple approximation is developed which gives good agreement with numerical results for the noise power.