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Phase locked loop angle modulation system with large modulation index

  • US 4,009,455 A
  • Filed: 09/11/1975
  • Issued: 02/22/1977
  • Est. Priority Date: 09/12/1974
  • Status: Expired due to Term
First Claim
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1. An angle modulation system comprising:

  • means for supplying a modulating signal;

    a voltage controlled oscillator means operating at an oscillation frequency controlled by an applied signal, said voltage controlled oscillator naturally having an undesired side band;

    frequency dividing means for dividing the output frequency of the voltage controlled oscillator with a specific frequency dividing ratio;

    means for supplying a reference signal of a specific frequency;

    phase comparison means jointly responsive to the output of the frequency dividing means and the reference signal from the reference signal supplying means;

    frequency selection means in a path extending from the voltage controlled oscillator means, through the frequency dividing means, to the phase comparison means, said frequency selection means eliminating said undesired side band component from the output of the voltage controlled oscillator means;

    adding means for adding the modulating signal and the output signal of the phase comparison means, and for applying the resulting signal to the voltage controlled oscillator means;

    carrier elimination means in a path extending from the phase comparison means to the adding means for eliminating a frequency divided carrier component; and

    means for deriving an angle-modulated signal from the output of the voltage controlled oscillator.

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