Abstract: In a differential-detection demodulator circuit, a PSK modulated signal is compared with a locally oscillated signal to obtain a phase difference between the two signals, whereupon the phase difference is demodulated. A phase detector circuit of the digital type outputs the phase difference signal. The digital phase comparator circuit compares plural reference signals, which give predetermined delays to the locally oscillated signals having carrier frequencies, with the inputted modulated signals. Preferably, a pulse signal having a phase difference between the inputted modulated signal and the locally oscillated signal is produced, and the pulse width of this pulse signal is measured by a counter. By digitalizing the entire phase comparator, it is possible to realize demodulation with low electrical power consumption and simple circuit construction.

Abstract: In a demodulator circuit which is simple in construction, a PSK modulated signal is converted in frequency into a quasi-base band signal and is then subjected to complex separation. Partly since a phase angle sampled from a digital complex signal is supplied to a differential-detector circuit, and partly since the differential-detector circuit processes only the phase angle, the differential-detector circuit has a simple construction. As the detected phase difference between two successive symbol data, an error between a carrier wave contained in the modulated signal and a locally oscillated frequency on the receiving side is compensated and is outputted as a digital demodulated signal.