Self-biasing phase-locking loop system

Abstract

A phase-locked loop configured to cause an output signal to tend toward a desired output frequency based on an applied reference signal. In a first configuration, the phase-locked loop includes a voltage controlled oscillator operatively coupled with a bias generator. The voltage controlled oscillator is configured to produce the output signal in response to a VCO current generated via application of a biasing signal from the bias generator. The VCO current produces a regulated VCO voltage within the voltage controlled oscillator, and the bias generator is configured so that the regulated bias generator voltage matches the regulated VCO voltage free of any direct coupling between the bias generator and the regulated VCO voltage. In another configuration, the phase-locked loop includes a charge pump system having semiconductor components that correspond to only a portion of a voltage controlled oscillator associated with the loop. The semiconductor components are selected to provide the charge pump system with an effective impedance that is matched to an effective impedance of the voltage controlled oscillator. According to this aspect of the invention, the phase-locked loop further includes a bias generator configured to use the effective charge pump impedance to bias the charge pump system and thereby produce within the charge pump system a charge pump current of equal density to a VCO current used to drive the voltage controlled oscillator. In other configurations, the phase-locked loop includes isolated charge pumps and/or a charge pump configured to provide a spread spectrum output.