Method and apparatus for quadrature modulation
First Claim
Patent Images
1. A method of transmitting a quadrature amplitude modulated signal comprising the steps of:
- quadrature modulating first and second signals onto a first subcarrier, quadrature modulating third and fourth signals onto a second subcarrier,quadrature modulating said first and second quadrature modulated subcarriers onto a carrier, andtransmitting said quadrature modulated carrier,
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Abstract
A quadrature amplitude modulation system utilizes two subcarrier signals, each quadrature modulated with information signals which are quadrature modulated onto the RF carrier. This provides a hole in the center of frequency spectrum, permitting carrier and bit sync signals can be provided in the center area of the signal spectrum.
113 Citations
11 Claims
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1. A method of transmitting a quadrature amplitude modulated signal comprising the steps of:
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quadrature modulating first and second signals onto a first subcarrier, quadrature modulating third and fourth signals onto a second subcarrier, quadrature modulating said first and second quadrature modulated subcarriers onto a carrier, and transmitting said quadrature modulated carrier, - View Dependent Claims (3, 4)
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2. A method of transmitting a quadrature amplitude modulated signal comprising the steps of;
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quadrature modulating first and second signals onto a first subcarrier quadrature modulating third and fourth signals onto a second subcarrier, providing a DC component with one of said quadrature modulated subcarriers for producing a pilot carrier, quadrature modulating said quadrature first and second quadrature modulated subcarriers onto a carrier, and transmitting said quadrature modulated carrier.
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5. A method of transmitting a quadrature amplitude modulated signal, comprising:
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reading from memory first and second prototype pulses each including a subcarrier component, summing said first and second prototype pulses to produce a first quadrature modulated subcarrier, reading from memory third and fourth prototype pulses each including a subcarrier component, summing said third and fourth prototype pulses to produce a second quadrature modulated subcarrier, quadrature modulating a carrier with said first and second quadrature modulated subcarriers, and transmitting said quadrature modulated carrier. - View Dependent Claims (7)
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6. A method of transmitting a quadrature amplitude modulated signal comprising:
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reading from memory first and second prototype pulses each including a subcarrier component, summing said first and second prototype pulses to produce a first quadrature modulated subcarrier, reading form memory third and fourth prototype pulses each including a subcarrier component, summing said third and fourth prototype pulses to produce a second quadrature modulated subcarrier, quadrature modulating a carrier with said first and second quadrature modulated subcarriers, summing an offset with one of said summed pulses prior to quadrature modulating said carrier, and transmitting said quadrature modulated carrier,
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8. An apparatus for transmitting quadrature modulated signals comprising:
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means for quadrature modulating first and second signals on a first subcarrier, means for quadrature modulating third and fourth signals onto a second subcarrier, means for quadrature modulating said first and second subcarriers onto a carrier, and means for transmitting said quadrature modulated carrier.
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9. An apparatus for transmitting quadrature modulated signals comprising:
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means for quadrature modulating first and second signals on a first subcarrier, means for quadrature modulating third and fourth signals onto a second subcarrier, means for summing a sync signal with one of said subcarriers, means for quadrature modulating said first and second subcarriers onto a carrier, and means for transmitting said quadrature modulated carrier. - View Dependent Claims (10, 11)
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Specification