Phase synchronization system

Abstract

A phase synchronization circuit for processing a received signal, the phase of which is detected by a first reference carrier from a fixed oscillator and a second reference carrier orthogonal to the first reference carrier. Two baseband signals are thus obtained and sampled with a certain period. Converters convert these two signals into digital values. Phase and amplitude values at each sample point are obtained from these digital values orthogonal to each other. The frequency and phase differences between the received signal and each of the first and second reference carriers are estimated by an optimization method by utilization of pluralities of phase and amplitude data obtained with a fixed period of time. The voltage-controlled oscillator and the phase shifter are controlled with the estimated values for generating a recovered carrier of a phase synchronized with the received signal. A circuit is provided in which the hysteresis of frequency and phase differences are stored at the time of current estimation. The stored values and currently-estimated values are compared with each other. On the basis of the results of the comparison of these values, the received signal is analogized. The numbers of data samples for use in the estimation of the frequency and phase differences are made variable according to the result analogy, thereby achieving an optimum phase synchronization in accordance with the state of the received signal.