Analysis of FM Systems with Co-Channel Interference Using a Click Model

Rice's click model for ideal FM detection is applied to systems with co-channel interference. Output noise terms consist of a high signal-to-noise ratio (SNR) term due to noise alone, a term due to the desired signal beating with the interferer, and a term due to the clicks. Click rates are determined with and without modulation and it is shown that in the computation of noise due to clicks the interferer can be treated as a simple sinusoid [i.e., an unmodulated carrier] Plots are given for detected SNR versus carrier-to-noise (CNR) with signal-to-interferer ratio (SIR) and modulation index as parameters. The effect of signal suppression is analyzed and for the range of parameters used in this paper it is found to be negligible.