VCO tuning curve compensated charge pump current synthesizer

摘要

A system provided for controlling an output frequency of a voltage controlled oscillator relative to a reference frequency. A method includes the steps of detecting a phase error between a divided output of the voltage controlled oscillator and the reference frequency, pumping a frequency control input of the voltage controlled oscillator with the phase error and adjusting a pumping gain based upon a magnitude of the frequency control input to the voltage controlled oscillator. The apparatus includes a phase detector adapted to detect the phase error between the divided output of the voltage controlled oscilator and the reference frequency and a charge pump adapted to pump the frequency control input of the voltage controlled oscillator with the phase error. The apparatus also includes a gain controller adapted to adjust the pumping gain based upon the magnitude of the frequency control input to the voltage controlled oscillator.