| 摘要 |
PURPOSE:To easily pull in frequency and to attain stable demodulation even when a transmission speed is low by providing a sweep/track control signal generating part, etc., and varying a range for the frequency locking. CONSTITUTION:When a phase state change signal (INIT signal), which is outputted when a phase state is changed, is inputted to a sweep/track control signal generating part 7, a sweep control signal is inputted to loop filter 5. As a result, a voltage control oscillator 6 goes to a sweep mode and the dislocation of phase difference sweeps -45 deg. to 45 deg.. A frequency locking range F is set large). When the range includes phase difference '0', a track control signal is outputted from the generating part 7 and the oscillator 6 cancels the sweep mode. Then, the phase difference is caused to be completely '0' on the basis phase deviation signal from a phase detecting circuit 4. When synchronization is completed, the 'F is changed to a value which is smaller than the value up to the present. Thus, even when the transmission speed is low, the frequency pull-in can be easily executed and the stable demodulation can be executed. |
