| 摘要 |
PURPOSE:To reducce phase jitter and to eliminate the replacement of demodulation data between both channels I and Q, by detecting the power of both channels I and Q, and making a cmparison between the both, and unlocking a phase- locked circuit according to the comparison result. CONSTITUTION:An unbalanced 4-phase phase-modulated UQPSK waves inputted from a terminal 1 of an I and a Q channel (CH) are applied synchronous detection detected in synchronous detectors 2 and 3 with reference carrier waves from a voltage-controlled oscillator 14 and a phase shifter 15, and they are led to a reverse modulation part 18 equipped with an attenuator 9 on a side QCH through voltage comparators 4 and 5. Outputs of the detectors 2 and 3 are supplied to power detecting circuits 108 and 109 to detect the power, and a comparing circuit 110 make a comparison between the both. The output of the circuit 110 is added to the output of a loop filter 13 by an adder 107 of a phase-locked circuit 19. When the power of the circuit 109 is greater, the adder 107 unlocks the phase of an oscillator 14 and only when the phase difference between the carrier of the UQPSK wave and a regenerated reference carrier from a terminal 17 is 0 and pi, is phase locked and phase jitter is reduced. |
