FM demodulator has shift register delaying FM carrier - and phase comparator producing pulse number proportional to instant frequency of carrier

摘要

The FM demodulator has a phase comparator (KG) which compares the FM carrier with the delayed FM carrier and it supplies an averager. A shift register (SR) is used to produce a delay that is dependent on the number of register stages and the period of its clocking pulses. The number of pulses appearing at the phase comparator output in unit time is taken as a measure of the instantaneous frequency of the FM carrier. The averager (TP) is constructed from counters so that when a given end-value is reached a signal is released which corresponds to the received instantaneous frequency.