Low distortion filters for separating frequency or phase modulated signals from composite signals

Abstract From the Canadian patent

A circuit for separating FM signals from a composite signal utilizes a comb filter having successive frequency response s which span the frequency spectrum of the FM signal to be separated. The comb filter response is phase linear and defines the pass-band of the desired signal. A nonideal or phase nonlinear bandpass filter can be cascaded with the comb filter to attenuate out of band signals. The cascade combination of the comb filter and nonlinear bandpass filters is a cost effective substitute for the conventional, complicated phase linear bandpass filter having a boxcar frequency response traditionally used to separate FM signals.