Blind Estimation On Detection And PN Sequence Of Non-periodic DSSS Signals

Because of its strong anti-interference,low intercept rate,good concealment of the signal and code division multiple access,Direct Sequence Spread Spectrum communication is widely used in military confrontation and civilian communications.Electronic countermeasures in military communication and in 3G in civil communication are the most representative applications.In order to realize signal detection of parameter and estimation of the PN code for the non-periodic Direct Sequence Spread Spectrum under the low SNR,algorithm applied to non-cooperative non-periodic DSSS detection and estimation of parameter,PN code sequence is studied and argumented.Firstly,Spread Spectrum Communication signal model is established,and the non-periodic PN code sequence and two ways of data segmentation for spread spectrum signal are studied In order to detecte and estimate parameter for DSSS/BPSK,the algorithm combined cyclic spectrum and collection average signal is studied.Noise is suppressed,so carrier information and code rate can be get more accurately.It lay a good foundation for the estimation of the PN code.Secondly,in order to blindly estimate PN code of the non-periodic spread spectrum signal,the algorithms combined two kinds of data segmentation preprocessing segmentation and eigen-decomposition are studied.In order to estimate delay values under asynchronous,the sliding window technology is mainly used.when modulation ratio is greater than 3,first of all the delay value appearred at maximum probability is calculated and all vectors are cut uniformly.Then,in order to blindly estimate PN code of the non-periodic spread spectrum signal,the algorithms combined two kinds of data preprocessing segmentation and subspace tracking are studied.And a new algorithm which Space tracking algorithm based on variable forgetting factor was proposed.The feature of new algorithm is small computational complexity,small storage capacity,good real-time performance,ease of hardware implementation.Estimation of PN code for non-periodic DSSS signal sequence blindly can be realize under low SNR.Finally,the segmentation Eigen-decomposition,segmentation subspace tracking andimproved algorithm based on variable forgetting factor under synchronous and asynchronous is comparised.The performance of the improved algorithm are studied.The signal-to-noise volume limit is reduced and good convergence can be seen from the simulation results.