Suppression of Interchannel Interference in FM Receivers

In this work an FM detector capable of suppressing the degradation in receiver performance due to the presence of an interfering signal is presented. Optimum receiver structures based on maximum-a-posteriori estimation procedures are first theoretically derived and then a practical demodulator based on the optimum receivers is examined. The receiver consists of two phase-locked loops (PLL) cross coupled in such a manner as to permit one PLL to lock on to and track the stronger received FM signal while the other loop tracks the weaker of the two received FM signals. The detector has the capability of demodulating both the desired received FM as well as the interferer even for the case when both signals are co-channel. Experimental results demonstrating such capability even in the presence of strong input gaussian noise are presented along with a computer simulation study examining the transient acquisition behavior of the cross coupled PLL receiver structure. (Author).