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Simplified frequency scheme for coherent transponders

  • US 4,513,447 A
  • Filed: 12/13/1982
  • Issued: 04/23/1985
  • Est. Priority Date: 12/13/1982
  • Status: Expired due to Term
First Claim
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1. A coherent transponder for a communications system, including a transmitter and a receiver operating at different frequencies, comprising:

  • a first numerically controlled oscillator coupled to the receiver for controlling the operating frequency in at least a portion thereof;

    a second numerically controlled oscillator coupled to the transmitter for controlling the operating frequency in at least a portion thereof;

    a fixed frequency source;

    a means for comparing the controlled operating frequency of the receiver to a predetermined frequency derived from said fixed frequency source and providing a digital frequency control word representative of any error in the controlled operating frequency;

    means coupling clock signals from said fixed frequency source and the frequency control word to said first and second numerically controlled oscillators for controlling said first and second numerically controlled oscillators to provide the different operating frequencies in the transmitter and receiver while maintaining coherence.

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