| 摘要 |
PROBLEM TO BE SOLVED: To adjust a frequency variable range with high precision and to produce a device relatively inexpensively by providing an adjustment circuit for adjusting a variable frequency range of a voltage control oscillator(VCO) and adjusting an output of a low-pass filter in a specific oscillation frequency of the VCO to a predetermined value. SOLUTION: A output signal of a VCO 10 is phase compared with a signal which is frequency divided at an arbitrary frequency rate N and a referential signal from a referential oscillator 62, the comparison result is converted into a DC voltage by a low-pass filter 50 and applied to a variable resonance circuit such as a variable capacity diode of the VCO 10. Thus, the VCO 10 outputs a signal of a frequency equal to N-multiple of the frequency division rate of a variable frequency divider 61 of a PLL circuit from an output terminal 15. Next, in an adjustment circuit 70, a parameter of an additional resonance element of the resonance circuit of the VCO 10 is adjusted so that a control voltage of the low-pass filter 50 of the PLL circuit becomes an expected value when, for example, an output frequency from the VCO 10 is at an upper limit of a variable range.
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