DEMODULATION CIRCUIT

摘要

Disclosed is a demodulation circuit for use in a heterodyne receiver for stably demodulating a carrier-suppressed double-sideband signal such as a 2-phase or phase PSK signal. The demodulation circuit comprises a reference oscillator oscillating at a frequency corresponding to an intermediate frequency, and the frequency difference between the reference frequency and the input frequency is detected by a costas loop, a signal indicative of the frequency difference being fed back to a local oscillator through a loop filter thereby stabilizing the intermediate frequency.