PSK DEMODULATOR HAVING AN AFC CIRCUIT

摘要

A PSK demodulator includes a voltage controlled oscillator responsive to a control signal and a frequency converter for frequency converting an input PSK signal as a function of the output of the voltage controlled oscillator, also included is a carrier recovery circuit for recovering a carrier wave from the output of the frequency converter means. A band-pass filter receives the recovered carrier wave; and a phase detector detects the output of the frequency converter as a function of the output of the band-pass filter and provides a demodulated signal. A phase comparator detects the phase difference between the input and output signals of the band-pass filter and a low-pass filter is responsive to the output of the phase comparator for providing the control signal. The PSK demodulator of the invention is essentially unaffected by frequency fluctuations of the input modulated waves.