Patent ID: 7091757

Claim:
A frequency generator, comprising: an oscillator that outputs differential signals which can control an oscillation frequency; and a frequency doubler to which the differential signals output from the oscillator are input, which doubles frequencies of the input signals and outputs differential signals, wherein: the frequency doubler comprises: a variable delay circuit; a differential multiplier provided with first differential input terminals to which the differential output signals of the oscillator are input via the variable delay circuit and second differential input terminals to which the differential output signals of the oscillator are input; a voltage-swing detection circuit that detects each magnitude of an amplitude in a positive phase and in a negative phase of differential outputs of the differential multiplier; and a control circuit that controls a delay time of the variable delay circuit based upon an amplitude difference detected by the voltage-swing detection circuit; and wherein the differential outputs of the differential multiplier are coupled to output terminals of the frequency generator.