Method and apparatus for quadrature modulation
AssigneeMotorola, Inc.
InventorClifford D. Leitch
Life of this patent
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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.
Claims11
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, and
- transmitting said quadrature modulated carrier,
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,
- 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.
A method of transmitting a quadrature amplitude modulated signal, comprising:
- 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.
A method of transmitting a quadrature amplitude modulated signal comprising:
- 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,
An apparatus for transmitting quadrature modulated signals comprising:
- 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.
An apparatus for transmitting quadrature modulated signals comprising:
- 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.
Dependencies are inferred from the claim text.