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Phase-locked loop stabilized by a crystal oscillator

  • US 4,310,805 A
  • Filed: 12/13/1979
  • Issued: 01/12/1982
  • Est. Priority Date: 12/13/1979
  • Status: Expired due to Term
First Claim
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1. Apparatus for providing at least one output frequency signal phase-locked to the frequency of an input signal, comprising:

  • a phase detector having first and second inputs and an output having a signal related to the difference in phase between the signals at the first and second inputs;

    input signal conditioning means receiving said input signal for providing a reference frequency signal to said first phase detector input;

    means connected to the phase detector output for filtering said phase detector output signal;

    means receiving the filtered output signal from the filtering means for generating a periodic waveform having a first frequency controlled by the magnitude of the filtered phase detector output signal;

    crystal controlled oscillator means for providing a signal at a second frequency;

    frequency-subtractive means having a first input receiving a sum-frequency signal and a second input receiving the second frequency signal for providing an output signal having a third frequency equal to the difference between said sum-frequency and second signal frequency;

    frequency-arithmetic means receiving the third frequency signal for synthesizing said at least one output signal and for providing a loop signal for coupling to the second input of said phase detector for causing said waveform generating means frequency to vary and lock the frequency of said at least one output frequency to said input signal frequency;

    said frequency-arithmetic means also providing a signal at a fourth frequency; and

    means receiving the waveform generating means output signal and said fourth frequency signal for adding the first and fourth frequency signals to provide the sum-frequency input signal to the first input of the frequency-subtractive means.

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