The Blind Estimation Of The PN Code Of The Signal Of Direct Sequence Spread Spectrum

Direct sequence spread spectrum is the main way of the spread spectrumcommunication, direct sequence spread spectrum has been widly used in thecommunication of modern military for its charactristics. Such as wide spectrum, lowpower spectral density, confidential, strong anti-jamming capability and can work in anextremely low SNR, but it is also difficulty for communications reconnaissance andelectronic counter, especially more difficult to detect the unknown direct sequencespread spectrum the in a complex environment background of noise. so direct sequencespread spectrum signal was considered to be a low signal intercept rate signal.This paper firstly introduces the basic principle of spread spectrum communication,including the knowledge of the direct sequence spread spectrum and pseudo-randomcode(hereafter as PN) theory. Secondly introduced the blind estimation of the PN codein details, including the PN code cycle and shape of PN code. We introdue severalmethods of the blind estimation of the PN code cycle, time-domain autocorrelation, thecepstrum and secondary processing of the power spectrum.and we do some simulationson the computer,then we introdue several methods of the blind estimations of the shapeof PN code, such as EVD, PASTd and LFSR. respectively in MATLAB simulation, andwe compares the advantages and disadvantages of these methods, the proposed methodis proved the feasibility, and we also do same analysis on the impact factors. such ascode length, SNR.