FM Suppression in a Mix-On-Self Loop

A theoretical analysis of the suppression of frequency modulation in parallel signal channels by the use of a Mix-On-Self (MOS) loop is presented here. The analysis includes the derivation of formulas which enable the prediction of FM suppression in both the reference and adjacent signal channels as a function of modulation frequency, modulation time delay in the loop bandpass filters, and modulation time delay between the parallel channels. Also included are experimental data demonstrating the use of an MOS loop and verifying the theoretical predictions for FM suppression in such a loop.