| 摘要 |
PURPOSE: A PLL(Phase Locked Loop) frequency synthesizer for compensating a variation of a frequency gain of a VCO(Voltage Controlled Oscillator) is provided to maintain constantly a gain characteristic by detecting and compensating the variation of the frequency gain of the VCO. CONSTITUTION: A PLL frequency synthesizer for compensating a variation of a frequency gain of a VCO includes a phase comparator, a loop filter, a VCO, a frequency divider, a voltage detector, and a controller. The phase comparator(201) is used for comparing phases of the first and the second signals with each other and outputting a phase error signal. The loop filter(203) is used for filtering the phase error signal and outputting a control signal. The VCO(205) is used for controlling a frequency gain of an output signal of the loop filter. The frequency divider(207) is used for dividing a frequency of an output signal of the VCO according to a frequency division ratio and applying the second signal to the phase comparator. The voltage detector(209) is used for detecting a control voltage from the control signal of the VCO. The controller(211) is used for calculating a gain characteristic of the VCO by using the frequency division ratio and controlling gains of the phase comparator, the loop filter, and the VCO.
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