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FRACTIONAL-N PHASE-LOCKED LOOP

  • US 20110175652A1
  • Filed: 01/20/2010
  • Published: 07/21/2011
  • Est. Priority Date: 01/20/2010
  • Status: Active Grant
First Claim
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1. A fractional-N phase-locked loop (PLL), comprising:

  • a first phase detector configured to compare first phase difference to generate a first error signal indicative of the first phase difference;

    a first voltage-controlled oscillator (VCO) configured to generate an output frequency according to the first error signal;

    a frequency multiplier configured to perform frequency multiplication on the output frequency to generate a multiplied signal, the frequency multiplier comprising a second phase-locked loop, thereby forming a second loop therein; and

    a first frequency divider configured to perform frequency division on the multiplied signal to generate a first divided signal, the first divided signal and a reference frequency being then compared by the first phase detector to determine the first phase difference;

    wherein the first phase detector, the first voltage-controlled oscillator, the frequency multiplier and the first frequency divider form a first loop.

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