Phase demodulator including variable phase shifter for controlling reference carrier

  • US 4,549,142 A
  • Filed: 10/21/1983
  • Issued: 10/22/1985
  • Est. Priority Date: 10/30/1982
  • Status: Expired due to Term
First Claim
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1. A phase demodulator comprising:

  • a first detector means for phase-detecting an input digital-signal-modulated carrier wave with a reference carrier wave supplied thereto;

    a variable phase shifter means for receiving said reference carrier wave and controlling its phase in response to a control signal;

    a second phase detector means for phase-detecting said input modulated carrier waves with the output of said variable phase shifter;

    means for recovering said reference carrier wave;

    multilevel discriminator means for multilevel discriminating outputs of said first and second detectors, said multilevel discriminator means comprising analog-to-digital (A/D) conversion means for receiving outputs of said first and second phase detector means and for providing corresponding first and second multi-bit digital signals, at least a portion of each multi-bit digital signal generated from each phase detector output representing demodulated data; and

    logic means for logically processing the output of the discriminator means and providing an orthogonality error signal as said control signal, said logic means comprising a first Exclusive OR (EOR) gate for receiving and combining selected bits from each of said multi-bit A/D converter output signals, a second EOR gate for receiving and combining different selected bits from each of said multi-bit A/D converter output signals, an adder means for adding the outputs of said first and second EOR gates to obtain said control signal.

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