Patent ID: 6693978
Filing Date: 2004-02-17
Classification: H03J,H04L

Abstract:
A carrier reproducing circuit for reproducing a carrier from a received phase shift keying modulation signal, comprising: reception CN ratio judging means for judging a reception CN ratio in accordance with the number of discrete values in excess of a predetermined threshold during a unit time period, the discrete values representing a signal point arrangement of a demodulation baseband signal generated when a carrier having a predetermined frequency difference from a modulation wave center frequency is supplied; frequency width converting means for setting a frequency width to be changed by one step, in accordance with the reception CN ratio judged by said reception CN ratio judging means; oscillation means for outputting a demodulation carrier by sequentially changing an oscillation frequency in accordance with the frequency width set by said frequency width converting means; and detecting means for detecting that the number of discrete values reduces to a value equal to or smaller than a threshold determined by the reception CN ratio judged by said reception CN ratio judging means, to prevent the oscillation frequency of said oscillation means from being changed in accordance with the frequency width.