Patent ID: 8531218

Claim:
A frequency generating system, comprising: a phase-locked loop, outputting a phase-locked clock, and controlling a voltage-controlled oscillator in the phase-locked loop by using a dual-path architecture, wherein the voltage-controlled oscillator comprises a varactor; and a control signal generation unit, coupled to the phase-locked loop, disposed in one of the dual paths, and providing an up voltage, a down voltage, or a middle voltage as a first control signal to control the voltage-controlled oscillator according to an up signal and a down signal of the phase-locked loop, wherein the control signal generation unit comprises: a transistor element, having a first terminal, a second terminal, and a control terminal, wherein the first terminal is coupled to the control terminal, and the second terminal is coupled to a ground voltage; and a bias current source, coupled to the first terminal of the transistor element, and providing a bias current to the transistor element, wherein the transistor element provides the middle voltage via the first terminal according to the bias current.