Research On Walsh Code Soft Spread Spectrum Signal Blind Despreading

Aiming at the blind despreading problem of Walsh code soft spread spectrum signal,this thesis is based on electronic warfare reconnaissance side,mainly studies the blind dispreading algorithm of Walsh code soft spread spectrum signal in Gaussian white noise environment,multi-tone interference suppression algorithm of Walsh code soft spread spectrum signal,blind separation algorithm of Walsh code soft spread spectrum multiple access signals and Walsh code soft spread spectrum signal denoising algorithm.The main work is summarized as follows:1.Aiming at the blind despreading problem of Walsh code soft spread spectrum signal in Gaussian white noise environment,a Walsh code soft spread spectrum signal blind despreading algorithm based on improved density peak clustering is proposed.The algorithm uses the weight Euclidean distance as the similarity measure of the data points and determines the truncation distance according to the overall distribution of the data points.The simulation results show that the improved algorithm can realize the blind despreading of Walsh code soft spread spectrum signal within a certain SNR range,and it has better stability and lower complexity.2.Aiming at the multi-tone interference suppression problem of Walsh code soft spread spectrum signal,an improved algorithm combining empirical mode decomposition and adaptive LMS filtering algorithm is proposed.The simulation results show that the improved algorithm can suppress the multi-tone interference of Walsh code soft spread spectrum signal within a certain SNR range.3.Aiming at the blind separation problem of Walsh code soft spread spectrum multiple access signals,the Fast-ICA algorithm is used to realize the blind separation of Walsh code soft spread spectrum multiple access signals.The simulation results show that the algorithm can realize the blind separation of Walsh code soft spreading multiple access signals within a certain range of SNR.4.Aiming at the noise reduction problem of Walsh code soft spread spectrum signal,a noise reduction algorithm based on improved empirical mode decomposition is proposed.The algorithm judges the demarcation point according to the difference of the convergence characteristics of the autocorrelation function of intrinsic mode function of the signal and the noise,and then performs wavelet filtering on the low-order intrinsic mode functions.The simulation results show that the algorithm can improve the performance of soft spread spectrum signal dispreading and blind separation of multiple access signals,and the bit error rate is low.