| 摘要 |
PURPOSE:To perform phase control stably and securely by placing a sweep signal generating circuit in a phase controlling state securely by operating it according to the loop state of a phase controlling circuit, and then by removing an unnecessary influence by disconnecting the sweep signal generating circuit. CONSTITUTION:A detector 11 detects whether the output frequency of a voltage- controlled oscillator 2 is within a phase controllable range or not. Then, an encoding counter 16 counts the output signal of a clock signal source 14 and the count data is converted into an analog signal by D/A conversion 18. This output signal is led to the control input terminal of the oscillator 2 through a switch 17. When the detector 11 generates an output that shows the frequency of the oscillator 2 is not in the phase controllable range, the output of the signal source 14 is supplied to the counter 16 to close a switch 17, and when the detection output shows that the frequency is in the phase controllable range, the switch 17 is opened under the control of a logical circuit 12. |
