Patent ID: 7443252
Filing Date: 2008-10-28
Classification: H03L

Abstract:
1. A calibration circuit for voltage-controlled oscillator (VCO), comprising: a control unit, with an output terminal outputting a first control voltage; a voltage-controlled oscillator, with a first input terminal receiving the first control voltage and outputting an oscillation frequency from its output terminal according to the first control voltage; a detection unit for detecting the oscillation frequency and outputting a detection result signal; a micro control unit, receiving the detection result signal and outputting an adjust signal according to the detection result signal; an adjuster unit for receiving the adjust signal and outputting a voltage-adjusting signal to a second input terminal of the VCO according to the adjust signal so as to adjust the oscillation frequency output from the VCO; a phase-locked loop (PLL) unit, with an input terminal receiving the oscillation frequency and outputting a second control voltage to the first input terminal of the VCO according to the oscillation frequency; a control voltage, detection unit, with an input terminal receiving the second control voltage and outputting a voltage-detection signal to the micro control unit according to the second control voltage, wherein the micro control unit outputs the adjust signal according to the voltage-detection signal; and a control switch set coupled to the output terminal of the PLL unit, the input terminal of the control voltage detection unit, the output terminal of the control unit, and the first input terminal of the VCO to control the connection between each of the units.