A Comparison of the Threshold Extension Capabilities of FMFB and Phase-Lock Loop Demodulators Employed in FDM-FM Communication Systems

A comparison of the threshold extension capabilities of the phase-lock loop and frequency modulation feedback (FMFB) demodulators is presented. The comparison, instead of being based upon the usual sinusoidal modulating signal type analysis, is based upon analyses which give consideration to the type of modulation that is of most interest to designers of frequency division multiplexfrequency modulation (FDM-FM) systems, i.e., to modulation by a band-limited noise-like signal. The basic operating parameters are defined in terms of rms values. The "clicks" analysis of Rice is utilized in the treatment for the two cases of ignoring and including the effects of modulation on the output noise clicks.