| 摘要 |
Provided is a frequency modulation circuit 1 for outputting a highly precise frequency-modulated signal regardless of variation in a characteristic of a VCO 15 . A correction value calculation section 17 calculates a correction value Vt<SUB>2 </SUB>based on a voltage value (Vtx-Vt<SUB>1</SUB>) resulting from subtracting a control voltage Vt<SUB>1</SUB>, which is generated by a control voltage generation section 11 , from a control voltage Vtx at which a sensitivity of the VCO 15 is maximized. A variable amplifier 18 amplifies the correction value Vt<SUB>2</SUB>. An addition section 13 outputs a control voltage Vt<SUB>3</SUB>, which results from adding the amplified correction value Vt<SUB>2 </SUB>to the control voltage Vt<SUB>1</SUB>, to the VCO 15 via a DAC 14.
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