Patent ID: 6870409
Filing Date: 2005-03-22
Classification: H03L

Abstract:
1. A frequency synthesizer comprising: a first divider adapted to receive and divide an oscillation frequency signal; a second divider adapted to receive a feedback frequency signal and divide the feedback frequency signal in response to a selection signal; and a division ratio controller comprising: an internal division ratio controller adapted to receive an output signal of the second divider, to divide the output signal of the second divider by a first internal division ratio to generate a first internal divider output signal, to divide the output of the second divider by a second internal division ratio to generate a second internal divider output signal, and to compare the first and second internal divider output signals to generate a first partial selection signal used to generate the selection signal; a sigma delta modulator adapted to receive a predetermined value K that is externally controlled, and to generate a second partial selection signal, in response to the first internal divider output signal; and a synthesizer adapted to synthesize the first and second partial selection signals and to generate the selection signal.