QPSK modulator or demodulator using subharmonic pump carrier signals
First Claim
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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Accused Products
Abstract
The present invention relates to a QPSK modulator or demodulator for modulating two different input bit streams with a subharmonic pump carrier signal to produce an appropriately encoded QPSK output signal. The subharmonic pump carrier signal used is a submultiple of a predetermined microwave or millimeter-wave carrier frequency. The QPSK modulator or demodulator is capable of being fabricated on a planar substrate using appropriate stripline filters and a mixer diode in each of an in-phase and quadrature signal path. A fin line arrangement, also capable of fabrication on the substrate, can be used to introduce an appropriately phased subharmonic pump carrier signal into each of the in-phase and quadrature signal paths before each mixer diode. Each mixer diode mixes the associated data bit stream and one of the two appropriately phased pump carrier signals to produce separate output signals which modulate along separate orthogonal axes, which output signals are combined to produce the QPSK modulator output signal.
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Citations
20 Claims
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1. A Quadrature Phase Shift Keying (QPSK) modulator comprising:
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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; andmeans for combining the output signals from the first and second mixers to generate a QPSK output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A Quadrature Phase Shift Keying (QPSK) demodulator comprising:
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an input terminal for receiving a QPSK input signal comprising a first and a second digital signal modulated along a first and a second orthogonal axis, respectively, with a predetermined microwave or millimeter-wave carrier signal; a first and second output terminal; means for dividing the QPSK input signal along a first and a second portion thereof for propagation along a first and a second rail, respectively; means for coupling an in-phase and a 90°
/n subharmonic pump carrier into the first and second rail, respectively, the pump carrier signal comprising a frequency which is a submultiple 1/n of the predetermined microwave or millimeter-wave carrier signal and is synchronized thereto, where n is an integer greater than 1;a first mixer disposed in the first rail for modulating the first portion of the QPSK input signal and the in-phase subharmonic pump carrier signal to generate a first output signal comprising only the first digital signal received in the QPSK input signal for transmission to the first output terminal; and a second mixer disposed in the second rail for modulating the second portion of the QPSK input signal and the 90°
/n subharmonic pump carrier signal to generate a second output signal comprising only the second digital signal received in the QPSK input signal for transmission to the second output terminal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification