CLOCK REPRODUCTION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a clock reproduction circuit reproducing a clock signal for data demodulation from an AM data multiplex modulation signal where a digital modulation signal is multiplexed in the same frequency band and same time as an AM modulation signal. SOLUTION: A band pass filter 1 extracts the carrier of the AM modulation signal from the AM data multiplex modulation signal where the digital modulation signal is multiplexed in the same frequency band and same time as the AM modulation signal. The oscillation frequency of a voltage control oscillator 5 is controlled by the output of a phase compactor 3 through a loop filter 4 and the oscillation output of the voltage control oscillator 5 is supplied to a direct digital synthesizer 6. The carrier extracted by the band pass filter 1 is phase-compared with the output of the direct digital synthesizer 6 in the phase comparator 3. The oscillation output of the voltage control oscillator 5 is synchronized with the carrier of the AM modulation signal and it is set to be the clock signal for data demodulation.