Patent ID: 7541849

Claim:
A phase locked circuit, comprising; a locked loop circuit including a phase comparator and a voltage controlled oscillator, wherein the locked loop circuit outputs an output signal of the voltage controlled oscillator, and wherein the phase comparator outputs a phase difference signal which corresponds to a phase difference between a reference signal input from an outside and a feedback signal based on the output signal of the voltage controlled oscillator, a frequency of the output signal of the voltage controlled oscillator is controlled on the basis of the phase difference signal, and at least one band pass filter part is provided to an output side of the locked loop circuit, wherein the locked loop circuit further includes a variable frequency divider, and wherein the variable frequency divider outputs the feedback signal obtained through dividing the output signal of the voltage controlled oscillator by a frequency division ratio which is changed on the basis of a switching signal for an output frequency, the switching signal coming from the outside, the locked loop circuit outputs the output signal having one of a plurality of mutually different frequencies predetermined on the basis of the switching signal for the output frequency, wherein the at least one band pass filter part has a pluralitv of band pass filters which correspond to the pluralitv of predetermined frequencies which are different from each other, and wherein a switching part which couples one of the pluralitv of band pass filters corresponding to the frequency of the output signal of the locked loop circuit to the voltage controlled oscillator is provided between the locked loop circuit and the at least one band pass filter part.