Methods and apparatus for spread spectrum modulation and demodulation
First Claim
1. A spreading and modulation method, comprising a step for spreading an original signal with spread spectrum codes and a step for modulating said spread data in a QPSK format, characterized in that:
- said spreading step comprises;
generating spread spectrum code chips by modulating an arbitrary pair of Golay complementary codes onto two orthogonal channels to obtain a complex complementary code as said spread spectrum code chips; and
spreading said original signal with said complex complementary code;
said complex complementary code comprises a real component and an imaginary component, which are orthogonal to each other, as an in-phase spread spectrum code and a quadrature spread spectrum code respectively; and
in the step of spreading said original signal with said complex complementary code, spreading an in-phase sub-channel of said original signal with said in-phase spread spectrum code and spreading a quadrature sub-channel of said original signal with said quadrature spread spectrum code.
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Abstract
The present invention relates to a method and an apparatus for spread spectrum modulation and demodulation using a special spread spectrum sequence, characterized in that Golay complementary codes are modulated onto orthogonal channels such that a corresponding complex complementary code is obtained. The signal spread by such complex complementary code has a low peak-to-average power ratio, a sound self-correlation property and cross-correlation property, which can well solve the problem of multi-access interference such that the communication performance of the entire system is improved.
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Citations
12 Claims
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1. A spreading and modulation method, comprising a step for spreading an original signal with spread spectrum codes and a step for modulating said spread data in a QPSK format, characterized in that:
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said spreading step comprises; generating spread spectrum code chips by modulating an arbitrary pair of Golay complementary codes onto two orthogonal channels to obtain a complex complementary code as said spread spectrum code chips; and spreading said original signal with said complex complementary code; said complex complementary code comprises a real component and an imaginary component, which are orthogonal to each other, as an in-phase spread spectrum code and a quadrature spread spectrum code respectively; and in the step of spreading said original signal with said complex complementary code, spreading an in-phase sub-channel of said original signal with said in-phase spread spectrum code and spreading a quadrature sub-channel of said original signal with said quadrature spread spectrum code.
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2. A despreading and demodulation method, comprising a step for demodulating a receiving signal in a QPSK format, a filtering step for filtering the QPSK demodulated signal so as to generate an in-phase baseband signal and a quadrature baseband signal, and a despreading step for despreading said in-phase baseband signal and said quadrature baseband signal, characterized in that:
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said despreading step includes the following steps; generating the same spread spectrum code chips as that of a transmitting side by modulating a pair of Golay complementary codes onto two orthogonal channels to obtain a complex complementary as said spread spectrum code chips; and despreading said in-phase baseband signal and said quadrature baseband signal with said complex complementary code. - View Dependent Claims (3, 4)
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5. A spreading and modulation apparatus, wherein said apparatus comprises:
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a complex complementary code generator for modulating an arbitrary pair of Golay complementary codes onto two orthogonal channels to obtain a complex complementary code; a spreading unit for receiving said complex complementary code from said complex complementary code generator and spreading an original signal with said complex complementary code; a local carrier generator for generating a pair of orthogonal sinusoid modulation signals for QPSK modulation; and a QPSK modulation unit for modulating the signal spread by said spreading unit in a QPSK format with a pair of said sinusoid modulation signals. - View Dependent Claims (6, 7)
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8. A despreading and demodulation apparatus, said apparatus comprises:
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a local carrier generator for generating a pair of orthogonal sinusoid modulation signals for QPSK demodulation; a QPSK demodulation unit for demodulating a receiving signal in a QPSK format with said pair of sinusoid modulation signals and outputting QPSK demodulated signals; a filtering unit for performing low-pass filtering upon said QPSK demodulated signals and outputting an in-phase baseband signal and a quadrature baseband signal; a local complex complementary code generator for modulating a pair of Golay complementary codes onto two orthogonal channels to generate the same complex complementary code as that of a transmitting side; a despreading unit for receiving said complex complementary code generated by said local complex complementary code generator, despreading said in-phase baseband signal and said quadrature baseband signal with said complex complementary code, outputting a main output signal containing an original signal of said transmitting side and outputting an auxiliary output signal. - View Dependent Claims (9, 10, 11, 12)
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Specification