Patent ID: 7486118

Claim:
A signal generating apparatus, for generating a synthesized signal according to an input signal, comprising: a phase-locked loop device, comprising: a phase detector, coupled to a reference oscillating signal, for generating a detected signal according to the reference oscillating signal and a feedback signal; a charge pump circuit, coupled to the phase detector, for generating a control signal according to the detected signal; a filter, coupled to the charge pump circuit, for filtering the control signal to generate a reference signal; a voltage controlled oscillator, coupled to the filter, for generating the synthesized signal according to the reference signal; and a divider, coupled to the voltage controlled oscillator, for dividing the synthesized signal according to a dividing factor for generating the feedback signal; a detecting device, coupled to the filter, for detecting the reference signal to generate a calibrating signal; a filtering device, coupled to the detecting device, for filtering the input signal and calibrating the input signal according to the calibrating signal to generate a filtered input signal; and a modulating device, comprising: a first switch, having a first input node for receiving a first factor setting, a second input node for receiving a second factor setting, and an output node, wherein in the calibration mode, the first switch provides a factor setting at the output node by coupling the output node to the first input node and then coupling the output node to the second input node; and a modulator, coupled to the filtering device, the first switch, and the divider, for modulating the filtered input signal in the normal operation mode and setting the dividing factor according to the factor setting received from the output node of the first switch in the calibration mode.