Patent ID: 7583773

Claim:
A frequency synthesizing device with automatic calibration for synthesizing a signal with a predetermined frequency, comprising: a voltage-controlled oscillator (VCO), which has a plurality of working bands, receives a coarse-tuned signal and a fine-tuned signal, and generates an output signal in the working band set by the coarse-tuned signal; a preliminary frequency divider unit, which receives the output signal and generates an intermediate signal by frequency dividing; a feedback frequency divider unit, which receives the intermediate signal and generates a feedback signal by frequency dividing; an automatic calibration unit, which receives an input signal and the intermediate signal and generates the coarse-tuned signal; a phase-frequency comparator, which compares the input signal and the feedback signal and generates an error signal according to the frequency and phase differences between the input signal and the feedback signal; and a low-pass filter, which filters the error signal and generates the fine-tuned signal.