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Research on Direct Sequence Spread Spectrum Signal Detection and Parameter Estimation

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Tutor: WuZhiLu
School: Harbin Institute of Technology
Course: Information and Communication Engineering
Keywords: DSSS,cyclostationarity,cyclic frequency,parameter estimation
CLC: TN914.42
Type: Master's thesis
Year:  2008
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Spread spectrum communication is adopted as a means of anti-interference. As a bran-new communication system, Spread spectrum communication has characteristic of Pseudo-Random, DS signals are always transmitted in low Signal-to-Noise environment. The conventional detection and estimation methods has to achieve 6dB or higher SNR to demodulate the DSSS signals, which have low PSD(Power spectrum density) and are always submerged in noise. To meet the future demand of electronic reconnaissance techniques, it is of great significance to study parameter estimation methods for DS-SS signals under low SNRs.Because the Direct Sequence Spread Spectrum signals have cyclic features, the cyclostationary theory has been applied in the detection and parameter estimation of the signals, which is accomplished by exploitation of cyclic feature of signal through cyclic spectral analyzers. This paper presents a modified DS signal cycle spectral analysis method after introduce of the theory of spectral correlation, and mainly deals with the estimation of the carrier frequency and the chip rate of DSSS signals. The algorithm makes full use of the performance characteristics domained by cycle frequency, it includes that: the burden of calculation is lessened greatly by the time aliasing processing, and it improves computational efficiency; a new methods based on cycle spectral density; in order to reduce the effect of random noise, we provide an average algorithm, it can make the spectral line be more obvious, and improved the SNR limit when estimating these parameters. The simulation results shows that SNR increases 2~3 dB than convetional algorithm with the same indicators. In order to supply the actual BPSK DS-SS signal to verify the algorithms, this dissertation present a design method of spread spectrum signal generator with adjustable muti-parameter in detail and signal detection circuit, includes the programme of hardware and the software processes.All studies in this paper proved that cyclic spectrum correlation technology is a effective and applied method for DS-SS signal detection.
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