Patent ID: 6930562

Claim:
An oscillator comprising a resonance circuit comprising: a first series connected circuit having an inductive impedance element; a second series connected circuit having a first capacitive impedance element, a first variable capacitive impedance element connected In series with said first capacitive impedance element and having a directional characteristic, and a second capacitive impedance element connected in series with said first variable capacitive impedance element; and a third series connected circuit having a third capacitive impedance element, a second variable capacitive impedance element connected in series with said third capacitive impedance element and having a directional characteristic, and a fourth capacitive impedance element connected in series with said second variable capacitive impedance element, and wherein said first series connected circuit, said second series connected circuit, and said third series connected circuit are connected in parallel, and said first variable capacitive impedance element and said second variable capacitive impedance element are oppositely connected with respect to either connection side of said second series connected circuit and said third series connected circuit, wherein variable capacities of said first variable capacitive impedance element and said second variable capacitive impedance element are externally controlled to be varied, and wherein the directional characteristic of said first variable capacitive impedance element and said second variable capacitive impedance element is a parasitic capacitance to around, and one or the terminals of each of said first and second variable capacitive impedance elements which has a larger parasitic capacitance to around is defined as a first terminal, while the other, which has a smaller parasitic capacitance to ground, is defined as a second terminal, and a first control voltage is applied to the first terminal of each of said first and second variable capacitive impedance elements, while a second control voltage is applied to the second terminal of each of said first and second variable capacitive impedance elements, said first control voltage and said second control voltage being adjusted to determine an oscillation frequency.