Blindly Detection And Parameters Estimation Of Direct Sequence Spread Spectrum Signal

Direct sequence spread spectrum communication system have been widely used in military and civil communication.Because it has many advantages such as anti-jamming capability,lowprobability of interception,multiple access capability and so on. With the development of the electron and information technology, the research of detection and parameter estimation of spread spectrum signals in non-cooperation communication has been a research hot spot.To meet the future demand of electronic reconnaissance techniques,it is of great signifieance to study parameter estimation methods for DSSS signals under low SNRs.The theory research on the detection and parameter estimation of spread spectrum signals in low signal to noise ratios(SNR) are accomplished.Firstly,the paper summarize the basic knowledge of spread spectrum communication.Secondly,the method of correlation detection approach and cyclic spectrum approach is used to detect the unknow signals.After the unkown signal is the signal of BPSK-DSSS,the square detection is used to estimate the the carrier frequency of the signals, the reprocessed power spectrum of DSSS is used to estimate the symbol period, the cyclic spectrum approach is used to estimate the chip rate,then according to the principle of the base-band signal of the DS signal can be achieved maximize through the accumulation of energy ,using the two-dimensional search algorithm,not only the problem of the start of synchronization of the PN code and information code is resolved successly,but also the number of information code in the long pseudo-code modulation is estimated.Finally,the PN sequence is recoveried based on the results of the length of the symbol period,the length of the code, the start of synchronization of the PN code and information code and the number of information code in the long pseudo-code modulation.Theory simulation results show that the methods mentioned are feasible to detect and estimate the PN sequence modulation DS signals whose PN sequence length is 31 to 1023.