Carrier injecting waveform-based modulation scheme for reducing satellite transponder power requirements and earth terminal antenna size
First Claim
Patent Images
1. A method of transmitting information comprising the steps of:
- providing a data signal representative of the information and comprising in-phase (I) and quadrature (Q) components;
biasing at least one of the I and Q components with an offset comprising a direct current (DC) offset;
generating a quadrature phase shift keyed (QPSK) waveform based upon a carrier signal; and
the at least one biased component; and
transmitting the QPSK waveform.
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Abstract
A QPSK modulation scheme uses a data spreading mechanism to rob a relatively limited portion of available transmitter power, and inject into the QPSK waveform a prescribed amount of carrier signal power, through which detection and non-regenerative extraction of the carrier at the receiver may be achieved without incurring a signal-to-noise degradation penalty. In addition, the injected carrier-based modulation scheme of the invention may employ high performance forward error correction coding, to significantly reduce the signal power required for achieving a very low energy per bit-to-noise density ratio (Eb/N0)—on the order of one to zero dB.
63 Citations
31 Claims
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1. A method of transmitting information comprising the steps of:
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providing a data signal representative of the information and comprising in-phase (I) and quadrature (Q) components;
biasing at least one of the I and Q components with an offset comprising a direct current (DC) offset;
generating a quadrature phase shift keyed (QPSK) waveform based upon a carrier signal; and
the at least one biased component; and
transmitting the QPSK waveform. - View Dependent Claims (2, 3, 4, 5, 6)
receiving the transmitted QPSK waveform; and
processing the received QPSK waveform to extract said carrier signal therefrom.
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3. A method according to claim 2, further including the step of:
processing the received QPSK waveform using the carrier signal extracted therefrom to derive said data signal.
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4. A method according to claim 3, wherein said data signal is encoded with a forward error correction code, and further including the step of decoding the encoded data signal to recover said information from said data signal.
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5. A method according to claim 4, wherein said forward error correction code is one capable of extending error rate performance to a value of energy per bit to noise density ratio (Eb/N0) less than 4 dB.
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6. A method according to claim 1, wherein generating the QPSK waveform comprises multiplying the carrier signal with the digital signal.
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7. A communication system comprising:
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a quadrature phase shift keyed (QPSK) waveform generator for generating a QPSK waveform based upon a carrier signal and a data signal, the data signal being representative of information to be transmitted and comprising I and Q components, and said QPSK waveform generator biasing at least one of the I and Q components with an offset prior to generating the QPSK waveform, the offset comprising a direct current (DC) offset voltage; and
a transmitter for transmitting the QPSK waveform produced by said QPSK waveform generator. - View Dependent Claims (8, 9, 10, 11)
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12. A method comprising the steps of:
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(a) providing a carrier signal comprising in-phase (I) and quadrature (Q) components;
(b) providing a data signal comprising I and Q components and biasing the I and Q components of the data signal with at least one offset comprising a spreading waveform; and
(c) combining the I and Q components of the carrier signal with the biased I and Q components of the data signal, respectively, to produce a quadrature phase shift keyed (QPSK) waveform. - View Dependent Claims (13, 14, 15, 16)
(d) transmitting the QPSK waveform produced in step (c);
(e) receiving the QPSK waveform transmitted in step (d);
(f) conducting non-regenerative recovery of the QPSK waveform received in step (e) to extract said carrier signal therefrom; and
(g) processing the QPSK waveform received in step (e) using the carrier signal extracted therefrom in step (f) to recover said data signal.
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14. A method according to claim 13, wherein said data signal contains information encoded with a forward error correction code, and further including the step (g) of decoding the encoded data signal to recover said information.
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15. A method according to claim 14, wherein said forward error correction code is a code capable of extending error rate performance to a value of energy per bit to noise density ratio (Eb/N0) less than 4 dB.
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16. A method according to claim 12, wherein combining comprises multiplying the I and Q components of the carrier signal with the biased I and Q components of the data signal, respectively.
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17. A method comprising the steps of:
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(a) receiving a quadrature phase shift keyed (QPSK) waveform having in-phase (I) and quadrature (Q) components of a carrier modulated with I and Q components of a data signal, at least one of the I and Q components of the data signal being biased by an offset comprising a direct current (DC) offset voltage; and
(b) conducting non-regenerative recovery of the QPSK waveform received in step (a) to extract said carrier signal based upon the offset. - View Dependent Claims (18, 19, 20)
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21. A method of transmitting information comprising the steps of:
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providing a data signal representative of the information and comprising in-phase (I) and quadrature (Q) components;
biasing at least one of the I and Q components with an offset comprising a spreading waveform;
generating a quadrature phase shift keyed (QPSK) waveform based upon a carrier signal and the at least one biased component; and
transmitting the QPSK waveform. - View Dependent Claims (22, 23, 24, 25, 26)
receiving the transmitted QPSK waveform; and
processing the received QPSK waveform to extract said carrier signal therefrom.
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23. A method according to claim 22, further including the step of:
- processing the received QPSK waveform using the carrier signal extracted therefrom to derive said data signal.
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24. A method according to claim 23, wherein said data signal is encoded with a forward error correction code, and further including the step of decoding the encoded data signal to recover said information from said data signal.
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25. A method according to claim 24, wherein said forward error correction code is one capable of extending error rate performance to a value of energy per bit to noise density ratio (Eb/No) less than 4 dB.
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26. A method according to claim 25, wherein generating the QPSK waveform comprises multiplying the carrier signal with the digital signal.
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27. A communication system comprising:
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a quadrature phase shift keyed (QPSK) waveform generator for generating a QPSK waveform based upon a carrier signal and a data signal, the data signal being representative of information to be transmitted and comprising I and Q components, and said QPSK waveform generator biasing at least one of the I and Q components with an offset prior to generating the QPSK waveform, the offset comprising a spreading waveform; and
a transmitter for transmitting the QPSK waveform produced by said QPSK waveform generator. - View Dependent Claims (28, 29, 30, 31)
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Specification