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Modulation noise estimation mechanism

  • US 7,460,499 B2
  • Filed: 01/16/2004
  • Issued: 12/02/2008
  • Est. Priority Date: 01/17/2003
  • Status: Active Grant
First Claim
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1. A method of testing an oscillator within a phase locked loop, said method comprising the steps of:

  • averaging phase error samples produced by said phase locked loop, wherein said phase error samples correspond to the phase noise of said oscillator;

    subtracting said average from a current phase error sample to yield a normalized phase error;

    generating an exception event if said normalized phase error exceeds a threshold, thereby indicating that the level of oscillator phase noise is not acceptable; and

    repeating said steps of averaging, subtracting and generating over a period of time and outputting a test failure indication if the number of exception events exceeds a maximum criterion and a test pass indication otherwise.

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