Patent ID: 6549079
Filing Date: 2003-04-15
Classification: H03L,Y10S

Abstract:
A feedback control system that is responsive to a reference signal which has a destination frequency, comprising:a voltage-controlled oscillator (VCO) that provides an output signal whose output frequency is responsive to a VCO control signal at a VCO control port; and a feedback control loop that generates a feedback signal with a feedback frequency which corresponds to said output frequency and that provides said VCO control signal; wherein said control loop includes: a) a phase detector that provides an error signal that corresponds to the phase difference between said reference signal and said feedback signal; b) a loop filter that is coupled to said VCO control port; c) a processor that responds to said reference signal and said feedback signal and provides a control signal which indicates when said feedback signal is within a predetermined acquisition range from said destination frequency; d) drive switches that, in absence of said control signal, couple an open-loop drive current to said loop filter to drive said feedback signal within said acquisition range and that, in presence of said control signal, terminate said drive current; and e) feedback switches that, in absence of said control signal, are decoupled from said error signal and that, in presence of said control signal, respond to said error signal and couple feedback currents to said loop filter to lock said feedback signal to said destination signal.