| 摘要 |
PROBLEM TO BE SOLVED: To control an output frequency to a prescribed optional value at input interruption of a reference frequency signal and prevent an upper limit width or a lower limit width of a phase lock range from being narrowed when the characteristic of a voltage controlled oscillator(VCO) is changed due to a temperature change or the like in a phase lock oscillation(PLO) circuit. SOLUTION: In the phase lock oscillation circuit provided with a phase comparator section 9-2 that compares a phase of a signal resulting from frequency-dividing an output signal from the voltage controlled oscillator(VCO) by a frequency divider 9-1 with a phase of an input signal having a reference frequency, with a low pass filter 9-3 and a DC amplifier circuit 9-4, input interruption of the reference frequency signal is detected, a reference voltage of the DC amplifier circuit 9-4 is changed to allow the DC amplifier circuit 9-4 to provide an output of a prescribed voltage so as to output a signal with a substantial center frequency from the voltage controlled oscillator(VCO). Also a reference voltage of the DC amplifier circuit 9-4 is changed in response to a characteristic change in the voltage controlled oscillator(VCO) so as to compensate an upper limit or a lower limit of a phase lock range. |
