Coherent phase demodulator for phase shift keyed suppressed carrier signals

摘要

Digital data, differentially phase shift keyed on a suppressed carrier, double side band transmission, is recovered by multiplying the input signal by a signal derived from regenerative feedback and consisting of the sum of a phase-coherent carrier and the recovered data signal. The phase-coherent carrier is derived by alternate phase reversals of the incoming carrier, produced by the polarity changes in the data. The phase- coherent carrier and the recovered data signal are components of the multiplier output and are separated by bandpass and low pass filters respectively, the output terminal of the low pass filter also being the data output terminal. When a carrier has been phase modulated with two distinct signals in quadrature, the received carrier is phase shifted to produce two signals in quadrature, then each of the resultant modulated carriers is demodulated as with the single signal carrier, using one common bandpass filter.