Frequency/phase locked loop clock synthesizer using an all...

Details Frequency/phase locked loop clock synthesizer using an all... Frequency/phase locked loop clock synthesizer using an all...

2008-03-25

2008-03-25

Ghayour, Mohammed (Department: 2611)

Pulse or digital communications

Synchronizers

Phase displacement, slip or jitter correction

Reexamination Certificate

active

10796331

ABSTRACT:
A frequency synthesizer, for integration in a low voltage digital CMOS process, controls a VCO using a dual loop structure including an analog loop and a digital loop. The digital loop includes an all digital frequency detector, which controls a center frequency of the VCO. The analog loop includes an analog phase detector and charge pump, which add phase coherence to the frequency controlled loop. The analog loop reduces the noise of the digital logic and VCO, and the digital control provides frequency holdover and very low bandwidth. The bandwidth of the digital loop is made smaller than the bandwidth of analog loop, and is preferably 200 times smaller. This parametric difference allows two separate control inputs to the VCO, one from the analog loop and one from the digital loop, with both inputs functioning relatively independently of each other.

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