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Digitally controlled phase locked loop system

  • US 4,802,009 A
  • Filed: 07/13/1987
  • Issued: 01/31/1989
  • Est. Priority Date: 07/13/1987
  • Status: Expired due to Term
First Claim
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1. Apparatus comprising:

  • a variable oscillator, responsive to a control signal for generating an oscillatory signal having a frequency determined by the value of said control signal;

    digital signal generation means including a digital oscillator for generating a plural-bit sampled data digital oscillatory signal having a frequency which approximates a predetermined nominal frequency;

    phase comparison means, coupled to said variable oscillator and to said digital signal generation means for generating a phase difference signal proportional to the difference in phase between said oscillatory signal and a single-bit digital signal representing a predetermined bit of said plural-bit sampled data digital oscillatory signal; and

    means, coupled to said phase comparison means and responsive to said phase difference signal for generating said control signal.

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