The Research Of Detection Of DS Signals And Parameter Estimation Of PN Sequence

The advantages of spread spectrum communication are as follows: low probability of intercept, good anti-fading and anti-multipath interference capability. It is widely used in military and civil communication. With the development of the electron and information technology, the blind de-spread of spread spectrum signals in non-cooperation communication has been a research hot spot. The blind detection and estimation of the chip rate and period of pseudo noise (PN) sequence are the precondition for the realization of blind de-spread.The theory research on the detection and estimation chip rate and period of PN sequence in low signal to noise ratios (SNR) are accomplished in order to put it into realization. Firstly, the paper summarize the basic knowledge of spread spectrum communication, point out that the baseband of DS signals are divided into short PN sequence modulation and long PN sequence modulation. Secondly, the delay and multiply approach is used to detect the DS signals and estimate the chip rate of PN sequence, and then an improved algorithm is proposed. The algorithm is deduced and the theory simulation results are given. Thirdly, the power spectrum reprocessing approach and cepstrum approach are used to estimate the period of PN sequence. A new method that a power spectrum reprocessing based on delay and multiply is introduced to estimate the period of long PN sequence modulation signals. The algorithm is deduced and the theory simulation results are given. Although the long PN sequence modulation has been used widely in the military communication with the good secrecy performance and restraint of jam between symbols, there is scarcely any research of long PN sequence modulation signals. So it is significant to research the estimation of long PN sequence modulation signals. Finally, the DS signals data acquisition project based on FPGA is given.Theory simulation results show that the methods mentioned are feasible to detect and estimate the short PN sequence modulation DS signals whose PN sequence length is 63 to 1023. The delay and multiply approach can be used to estimate the chip rate of long PN sequence modulation DS signals, and the improved algorithm of it is available in lower input SNR. The performance of the...