Key Technical Design Of Blind Demodulation Of Spread-spectrum Signal

Direct sequence spread spectrum (DSSS) communication systems has been widely used in these years for its advantage of wide spectrum, low working Signal-to-Noise ratio (SNR), anti-interference, anti-multipath effect, capability of CDMA, LPI and LPD. They are increasingly replacing conventional communication systems and obtaining extensively applications in modern military and commercial communication systems, for example, CDMA communication system, GPS , measuring and control system, satellite chain, identification of friend or foe and etc. Therefore, corresponding DSSS electronic counter technique becomes an urgent problem to solve in electronic warfare domain. Since the DSSS signal is always transmitted in seriously noisy environment, the blind demodulation of DSSS signal contains blind detection, blind parameter estimation and spreading sequences estimation of DSSS signals in lower SNR.In this thesis, we focus on the issue of blind detection, blind parameter estimation and spreading sequences estimation of DSSS signals interfered by strong Gaussian noise and the corresponding implemention of software,hardware design.In this case,the signal is non-cooperative,and often lacks adequate prior information.Firstly,we study and analyze the classical methods of blind detection, blind parameter estimation and spreading sequences estimation of DSSS signals,simulating the corresponding algorithms on PC and analyzing the possibility of its hardware implemention through the result of performance testing. Then we migrate the blind demodulation algorithms of DSSS/BPSK and process the entire system,designing the software on DSP platform, simulating on the hardware platform based on ADSP-21160 ,verifying and comparing the features and performance of corresponding algorithms.Finally, we aim at implementing high-performance algorithms of blind demodulation on the basis of a higher specification and design a hardware plan,including the selection of core devices and the design of module circuits, searching for suitable verification platform for the implemention of DSSS blind demodulation. The author grasps the various methods of blind demodulation of DSSS,and verifies its performance and effectiveness through a big number of simulations and software and hardware design, laying the foundation of ultimate achievement of establishing the DSSS blind demodulation testing system.