Abstract: A PLL-based frequency synthesizer is provided. In accordance with one aspect, a phase locked loop is provided that comprises a phase detector, a loop filter, a voltage controlled oscillator, and a feedback circuit. The phase detector has as inputs a reference frequency signal and a feedback signal. The phase detector is operable to generate a phase detection signal based on a comparison of phases between the reference frequency signal and the feedback signal. The loop filter is coupled to the phase detector for receiving the phase detection signal and generates an output voltage in response to the phase detection signal. The voltage controlled oscillator is coupled to the output voltage of the loop filter and generates a local oscillator signal. The feedback circuit is coupled to the local oscillator signal and generates the feedback signal. The feedback circuit comprises a sampling circuit.

Abstract: A closed-loop voltage-to-frequency (V/F) converter includes a voltage-controlled-oscillator (VCO) placed in a feedback voltage-locked loop (VLL). This converter achieves both wide bandwidth (for good phase-noise suppression) and good spurious rejection. The closed-loop V/F converter may be further configured in a larger phase-locked loop (PLL) to achieve accurate channel selection that is independent of temperature and process variations.