Direct Sequence Spread Spectrum Signal Detection And Parameter Estimation Techniques

Direct-Sequence Spread Spectrum transmitters (DS-SS) use a periodicalpseudo-random sequence (PN sequence) to modulate the baseband signal, and usingthe modulated signal to control the phase of carrier wave. In general, DS-SScommunication system adopts phase-shift-keying data modulation. In order to save thepower of emission and improve the efficiency of the transmitter, the double phasebalanced modulation controlling carrier wave is suggested.Because of the fast development in modern communication technology anddetection technology, research in military Communications Counter-Measures fieldhas been maken a great process. As a signal with large bandwidth and difficultdetection, spread spectrum signals have low probability of being intercepted andcaptured, strong discrimination ability, so the Spread Spectrum technology has gotwide usage upon mobile communications, radar, navigation and orientation. Peoplehave great interest in DS-SS detection and have developed the research work withhigh passion.At first, Spread Spectrum communication is adopted as a means ofanti-interference. As a bran-new communication system, Spread Spreadcommunication has characteristic of Pseudo-Random, DS signals are alwaystransmitted in low Signal-to-Noise environment. Compare to general communicationand settled frequency communication, DS communication has lower probability ofbeing intercepted and higher characteristic of anti-interference. Its specialities decidetwo sides: one side is that DS signals are difficult to find; the other side is that eventhough DS signals are detected, if the receiver doesn't know the spread sequence, thebaseband signal is impossible to recover. Classical signal detection and estimationtheory can't give effective detection and estimation. No matter what homotheticbetween DS signals and noise, DS signals are different from noise affirmatively. Sothe counterplot of DS signals should make full use of their difference in such field asTime field, Frequency field, Power Spectrum, Cepstrum, Spectrum Correlation, HighOrder Spectrum and Time-Frequency field to distinguish DS signals from othercommunication signals and noise. The anti-jamming of DS signals has two means:firstly, finding the existence of this signal; secondly, implementing effectiveinterference to Direct Sequence communication.