| 摘要 |
PROBLEM TO BE SOLVED: To generate a correct reproduction carrier synchronized with a demodulation carrier by detecting the phase difference of the demodulation carrier from the reproduction carrier at every one cycle of the demodulation carrier and changing a VCO voltage in a direction for reducing the phase difference. SOLUTION: Edge detecting equipments 1 and 2 detect the rising of respective demodulation carrier signal and a reproduction carrier signal. When the phase of the demodulation carrier signal leads more forward than that of the reproduction carrier signal, JK-FF3 becomes active by the phase difference. At the time of lag, in the same way, JK-FF4 becomes active by the phase difference. An up/down counter permits a count value to be up and down in accordance with the output signals of JK-FF3 and 4 and, in the meantime, loads an initial value by a signal from a demodulation carrier signal falling edge detecting equipment 5. The count value is D/A-converted and impressed on a voltage controlled oscillator 9, an oscillation frequency is divided and the reproduction carrier signal is obtained. Thus, the correct reproduction carrier is obtained in spite of a low reception level, increased jitters and the instantaneous phase difference change. |
