Carrier phase controller for a receiver of phase modulated signals

Claim 1

A carrier phase control apparatus used in a modem demodulating a quadrature amplitude modulated data signal comprising: a first phase shift means for shifting phase of output signals from an equalizer for correcting these signals for carrier frequency offset; a second phase shift means for shifting phases of output signals from said first phase shift means; a decision circuit for determining phase and amplitude of the output signal of said second phase shift means; a first phase detector for detecting a phase error depending on a phase jitter by using output signals of said first phase shifting means and said decision circuit; a second phase detector for detecting an error signal between the output signals of said second phase shifting means and said decision circuit; a predictive filter for predicting a carrier phase jitter using the output signals of said first phase detector and said second phase detector; a sinusoidal generator for producing sin and cos signals from the output signal of said predictive filter and for applying said cos and sin signals to said second phase shifting circuit; and a control circuit for controlling said first phase shifting circuit by using output signal of a loop filter receiving an output signal of said first phase detector.