| 摘要 |
A DDS 11a divides a frequency of a reference frequency signal (f0) and supplies the frequency-divided signal to a PD 12. The PD 12 receives a phase reference signal (fr) supplied from the DDS 11a as a reference phase. On the other hand, a DDS 11b sets the signal outputted from the VCO 13 to a frequency corresponding to the frequency set in the DDS 11a, and supplies this frequency-divided signal to the PD 12. The PD 12 detects the phase difference between the aforementioned phase reference signal and the frequency-divided signal and supplies the detected phase difference to the VCO 13. The VCO 13 corrects the phase fluctuation component on the basis of the detected phase difference so as to output an output signal (fv) in which the frequency is kept constant.
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