| 摘要 |
PROBLEM TO BE SOLVED: To provide a PLL circuit for reducing reference leakage by reducing the number of varactor diodes viewed from the VT terminal side of a VCO (voltage controlled oscillator). SOLUTION: The PLL circuit includes: a VCO switching circuit which sets a VCO control voltage output from a loop filter composing the PLL circuit and a VCO in relation with each other in advance, selects a corresponding VCO on the basis of the VCO control voltage of the loop filter and generates a switching signal for controlling connection between a VCO control voltage terminal of the VCO and an output terminal of the loop filter; a VT selection circuit which connects the VCO control voltage terminal of only the selected VCO to the output terminal of the loop filter on the basis of the switching signal and releases connection between the VCO control voltage terminal of the other VCO and the output terminal of the loop filter; and a plurality of VCOs having different oscillation frequency bands, respectively, wherein varactor diodes are connected to a control voltage terminal of each VCO. COPYRIGHT: (C)2011,JPO&INPIT
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