Study on a Low Noise Dual Phase Frequency Detector

In view of the present shortcomings of high phase noise of digital phase frequency detector,an analog phase detector with low phase noise is designed. Then a novel structure of dual phase frequency detector is proposed,which combines the digital phase frequency detector and the analog phase detector. In the phase lock loop,the digital phase frequency detector of the structure plays a major role in the frequency capture stage and phase locking stage,the analog phase detector plays a major role in the phase locked holding stage. The simulating result shows that the proposed structure has advantages of both digital phase frequency detector and analog phase detector,including broad capture range,fast locking speed and low phase noise.