Interchannel interference in FM and PM systems under noise loading conditions

One of the principal sources of interchannel interference in multichannel FM and PM systems is the dependence of the attenuation and phase shift of the transmission path on frequency. Here we study the interference produced by a simple kind of such a dependence, namely that due to a single echo. Besides being important in themselves, the results are of interest because they may be used to estimate the interference in other, more complicated cases. In this paper expressions are derived for the interchannel interference produced by echoes of relatively small amplitude. Several important special cases are studied in detail and curves that simplify the computation of the interference power are presented.