Patent ID: 7482881

Claim:
A synthesizer, comprising: a phase frequency detector to provide a phase difference based on a reference signal and a feedback signal; a charge pump to provide an output charge based on the phase difference; a loop filter to provide a control voltage based on the output charge; a voltage controlled oscillator to provide a synthesizer output signal based on the control voltage; a multi-modulus divider to divide a frequency of the synthesizer output signal by a value to provide the feedback signal; and a frequency change module to change a frequency of the reference signal that is provided to the phase frequency detector based on a low pass response of the synthesizer; wherein the frequency change module includes a switching module having a first input terminal and a second input terminal, wherein the first input terminal receives a first input signal having a first frequency, and wherein the second input terminal receives a second input signal having a second frequency that is different from the first frequency; and a spur reduction module that processes the first input signal to generate the second input signal; wherein the switching module selects the first input signal or the second input signal to be the reference signal, based on the low pass response of the synthesizer.