A note on the frequency distribution of an FM/FM signal

An approximate expression is derived giving the amplitude and phase of the individual frequency components of an fm/fm signal when the input is a sinusoid. The approximation is subject to the restrictions that the subcarrier frequency be large in comparison to the highest modulation frequency, and that the ratio of subcarrier deviation to subcarrier frequency be much less than unity. Some qualitative properties of the frequency spectrum are pointed out and discussed, and illustrations of representative single sub-carrier-frequency distribution are presented. Although subject to the above restrictions, the results are shown to be applicable to present day fm/fm telemetry techniques.