Patent ID: 7949072

Claim:
A circuit, comprising: a voltage controlled oscillator having a control voltage input and generating a frequency signal at a frequency f 1 set at least in part by the control voltage input; a polyphase filter circuit receiving the frequency signal and generating first and second +45/−45 degree offset signals at the frequency f 1 ; a first divider circuit receiving the frequency signal at the frequency f 1 and generating quadrature signals at a divided down frequency f 2 ; a quadrature mixer circuit receiving the first and second +45/−45 degree offset signals and the quadrature signals to generate a mixed signal at a frequency f 1 ±f 2 ; and a tracking filter operable to filter the mixed signal and output a first VCO output signal at the frequency f 1 ±f 2 wherein a resonance frequency fr of the tracking filter is tunable with changes in frequency setting of the voltage controlled oscillator to substantially match the frequency f 1 ±f 2 of the mixed signal.