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Dual mode automatic frequency control

  • US 5,163,159 A
  • Filed: 07/30/1990
  • Issued: 11/10/1992
  • Est. Priority Date: 07/30/1990
  • Status: Expired due to Term
First Claim
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1. A frequency control system operable to maintain a receiver oscillation frequency of at least one variable oscillator forming a portion of a receiver in a desired frequency relationship with an oscillation frequency of a modulated signal transmitted to the receiver and received thereat, said frequency control system comprising:

  • means for converting the modulated signal received by the receiver into an electrical signal of signal characteristics indicative of the modulated signal;

    analog signal detection circuitry coupled to receive the electrical signal generated by the means for converting and operative when the modulated signal comprises a frequency modulated signal, said analog signal detection circuitry having a phase detector for detecting frequency characteristics of the electrical signal indicative of the modulated signal and for generating a first reference signal of levels indicative of the frequency characteristics detected thereat;

    discrete signal detection circuitry coupled to receive the electrical signal generated by the means for converting and operative only when the modulated signal comprises a discretely-encoded, modulated signal, said discrete signal detection circuitry for determining frequency characteristics of the electrical signal indicative of the modulated signal and for generating a second reference signal of levels indicative of the frequency characteristics determined thereat; and

    means for altering the oscillation frequency of the variable oscillator responsive to the levels of the first frequency reference signal when the modulated signal comprises a frequency modulated signal and responsive to the levels of the second frequency reference signal when the modulated signal comprises a discretely-encoded, modulated signal, to maintain thereby the variable oscillator of the receiver in the desired frequency relationship with the oscillation frequency of the modulated signal.

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