Patent ID: 7944318

Claim:
A voltage controlled oscillator comprising: an inductor circuit that includes an inductor; a plurality of C-coupling type variable capacitance circuits each of which includes two variable capacitance elements connected in series at first terminals thereof, and two blocking capacitors having first electrodes connected to second terminals of said two variable capacitance elements, respectively, for blocking a direct current component, said plurality of C-coupling type variable capacitance circuits each being connected in parallel to said inductor circuit by second electrodes of said two blocking capacitors being connected to said inductor; at least one direct-coupling type variable capacitance circuit that includes only two variable capacitance elements connected in series at first terminals thereof and that is connected in parallel to said inductor circuit by second terminals of said two variable capacitance elements being directly connected to said inductor; a negative resistance circuit connected in parallel to said inductor circuit; and a reference voltage generating section for generating a plurality of reference voltages to be supplied to said plurality of C-coupling type variable capacitance circuits, respectively, wherein: the plurality of reference voltages are inputted to the second terminals of said variable capacitance elements of said plurality of C-coupling type variable capacitance circuits, respectively; a control voltage for feedback control of an oscillation frequency is inputted to the first terminals of said variable capacitance elements of said plurality of C-coupling type variable capacitance circuits and the first terminals of said variable capacitance elements of said at least one direct-coupling type variable capacitance circuit; and a variable capacitance circuit with a greatest threshold voltage about which a variation range of a capacitance value thereof is centered and a variable capacitance circuit with a smallest threshold voltage about which a variation range of a capacitance value thereof is centered are at least C-coupling type variable capacitance circuits of said C-coupling type variable capacitance circuits.