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Direct digital synthesizer driven phase lock loop frequency synthesizer with clean up phase lock loop

  • US 5,757,239 A
  • Filed: 01/08/1997
  • Issued: 05/26/1998
  • Est. Priority Date: 03/16/1995
  • Status: Expired due to Term
First Claim
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1. A frequency synthesizer comprising:

  • a frequency source for digitally generating a variable frequency signal;

    a first phase lock loop circuit having a first predetermined loop bandwidth coupled to said frequency source;

    a second phase lock loop circuit having a second predetermined loop bandwidth greater than said first predetermined loop bandwidth coupled to said first phase lock loop circuit;

    a power splitter disposed between said frequency source and said first phase lock loop circuit, said power splitter having an input and first and second outputs, said power splitter input coupled to an output of said frequency source and said power splitter first output coupled to said first phase lock loop circuit;

    a first switch, responsive to a first switch control signal, disposed between said first phase lock loop circuit and said second phase lock loop circuit;

    a summer disposed between said first switch and said second phase lock loop circuit, said summer having first and second inputs and an output, said summer first input coupled to said first switch and said summer output coupled to said second phase lock loop circuit; and

    a second switch, responsive to a second switch control signal, coupled to said power splitter second output and said summer second input.

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