Patent ID: 7292108

Claim:
A voltage controlled oscillator comprising: an oscillating transistor; and first and second inductance elements which are connected in series and provided between an output terminal of the oscillating transistor and a high frequency ground point, wherein a fundamental wave is output from the output terminal of the oscillating transistor and a harmonic wave is output from a connecting point between the first inductance element and the second inductance element, respectively, wherein the first inductance element is provided at the side of the high frequency ground point, the second inductance element is provided at the side of the output terminal of the oscillating transistor, a first resonance circuit is constructed by connecting a first capacitive element to the first inductance element in parallel, a second resonance circuit is coupled to a base of the oscillating transistor, the first resonance circuit is operable to resonate with the frequency of a specific harmonic wave included in the oscillating signal a buffer amplifier for amplifying the oscillating signal is provided, and the connecting point between the first inductance element and the second inductance element is coupled to an input terminal of the buffer amplifier, the buffer amplifier has an amplifying transistor whose emitter is grounded, and a collector of the amplifying transistor is applied with a voltage from the emitter of the oscillating transistor, and a collector of the amplifying transistor is connected to the emitter of the oscillating transistor through an inductance element that is operable to suppress harmonic wave.