JPS6460046A - Fsk demodulating circuit - Google Patents

Abstract

PURPOSE:To eliminate a phase shifter on the circuit constitution of a phase detector and to decrease the generation of an error based on a noise, etc., by extracting the phase information of the four points of the rising and falling edges of a signal and executing a majority processing concerning a result. CONSTITUTION:The titled circuit provides a phase detecting means 1 to obtain two signal outputs to be orthogonalized, whose phase relation is changed in correspondence to a modulating code by multiplying two carrier waves to be mutually orthogonalized to an FSK modulating wave, sampling means 21-24 to obtain four binary signals by respectively sampling one signal value with the rising and falling edges of the other one of the two signal outputs and a majority deciding means 3 to execute the majority decision of the four binary signals and to generate the output of the decided result. A holding means 4 is also provided to output the output of the decided result as a demodulating signal when the majority decision is executed and to hold a just preceding decided value when '1' and '0' are in the same number in the majority decision. Thus, since the phase shifter is not used on the circuit constitution of the phase detector, realization goes to be easy and the generation of the error due to the noise, etc., is decreased.