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QPSK modulator or demodulator using subharmonic pump carrier signals

  • US 4,612,518 A
  • Filed: 05/28/1985
  • Issued: 09/16/1986
  • Est. Priority Date: 05/28/1985
  • Status: Expired due to Term
First Claim
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1. A Quadrature Phase Shift Keying (QPSK) modulator comprising:

  • a first and a second input terminal for receiving a first and a second digital signal, respectively, for propagation along a respective first and second rail;

    means for coupling an in-phase and a 90°

    /n subharmonic pump carrier signal into the first and second rail, respectively, the pump carrier signal comprising a frequency which is a submultiple (1/n) of a predetermined microwave or millimeter-wave carrier frequency, where n is an integer greater than 1;

    a first mixer disposed in the first rail for modulating the first digital signal and the in-phase subharmonic pump carrier signal to generate an output signal modulating along a first axis;

    a second mixer disposed in the second rail for modulating the second digital signal with the 90°

    /n subharmonic pump carrier signal to generate an output signal modulating along a second axis which is orthogonal to the first axis; and

    means for combining the output signals from the first and second mixers to generate a QPSK output signal.

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