FREQUENCY VARIABLE RESONANCE CIRCUIT AND VOLTAGE CONTROLLED OSCILLATOR IMPLEMENTED BY THE SAME, IN WHICH RESISTANCE OF RESONANCE CIRCUIT IS CONTROLLED

摘要

PURPOSE: A frequency variable resonance circuit and a voltage controlled oscillator implemented by the same are provided to improve high frequency characteristic by reducing resistance of a resonance circuit and to reduce phase noise by increasing fidelity. CONSTITUTION: A frequency variable resonance circuit includes an inductance device, a frequency variable circuit and a resonance bandwidth selection circuit. The inductance device has a fixed inductance value. The frequency variable circuit connected to the inductance device in parallel is composed of at least one varactor diode pairs whose capacitor value is changed by a first control signal, and it changes oscillation frequency. The resonance bandwidth selection circuit is provided with at least pair of capacitance devices(C51-C52,C53-C54,C55-C56) and at least one pair of differential switching devices(M51-M52,M53-M54,M55-M56). And, the differential switching devices(M51-M52,M53-M54,M55-M56) connect the corresponding pair of capacitance devices(C51-C52,C53-C54,C55-C56) to the inductance device in response to a second control signal.