Patent ID: 7072264

Claim:
A voltage controlled oscillator (VCO), comprising: a digital VCO that outputs an oscillating frequency clock based on a digital frequency control input signal; a phase modulator to which said oscillating frequency clock outputted from said digital VCO is inputted; and a frequency band limiting means to which an output from said phase modulator is inputted, wherein: said digital VCO also outputs a phase difference lower than an output cycle resolution decided by a master clock frequency to operate said digital VCO at the same timing of the output of said oscillating frequency clock, said phase modulator makes side-band components of the output from said digital VCO move from positions near a fundamental frequency to farther bands by modulating the phase of the output from said digital VCO based on said phase difference, and said frequency band limiting means eliminates said side-band components moved to said farther bands by a frequency band limitation.