| 摘要 |
A tuning circuit is formed of inductors connected in series, voltage-controlled variable capacitance means connected in parallel to the inductors, switch means connected in parallel to one of the inductors and capacitance means connected in parallel to another of the inductors, and the resonance frequency of a resonant circuit of the inductor and the capacitance means is set higher than the resonance frequency of the tuning circuit. When the switch means is turned off to change the frequency of the -tuning circuit to the lower frequency band, the frequency variable ratio of the tuning circuit becomes large and when the switch means is turned on to change the frequency to the higher frequency band, such frequency variable ratio becomes small, and the frequency variable width of the lower frequency band can be set almost equal to the frequency variable width of the higher frequency band by adequately selecting the capacitance of the capacitance means.
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