A method for calculating distortion of an FM signal by a passive network

Linear passive networks cannot manufacture RF signals but they can accord a different treatment to signals of different frequencies, and it is this property which enables some of them to modify an FM signal in a way which results in apparent addition of harmonics and crossmodulation products of the baseband frequencies. The author attempts to show how this comes about and to provide ways of calculating the magnitudes of the various modulation byproducts which can be added to an FM signal by a given passive network