Patent ID: 7839229

Claim:
A voltage-controlled oscillator, comprising: a differential Colpitts oscillator including a pair of bipolar transistors and a resonator to vary resonant frequency based on an input control voltage; a pair of transformers each having a respective primary inductor and a respective secondary inductor coupled by a mutual inductance, each said primary inductor being connected at a first end thereof to an emitter terminal of an associated one of the pair of bipolar transistors; an impedance-matching circuit connected to the respective secondary inductors of the pair of transformers; and a current source, wherein respective second ends of said primary inductors are coupled together and to the current source, and wherein differential alternating current outputted from the differential Colpitts oscillator is inputted to the respective primary inductors, and an output signal is outputted from respective first ends of each of the secondary inductors of the pair of transformers.