Research And Realization Of DSSS Communication System Based On Matched Filter

As the core of the third generation mobile communication systems, CDMA greatly enhance the communication quality and system capacity and has been widely used in civilian communications. CDMA is based on spread spectrum technology, and the spreading sequence synchronization is one of the key technologies of direct sequence spread spectrum communication system, so its in-depth study is necessary.On the basis of the basic principles of DS communication system as well as the spreading sequence synchronization of in-depth study and research, the author has made the detailed design of DS communication system. Basis for the design, using top-down design methodology, using the verilog hardware description language, the author especially completed the modules of send, receive and sequence synchronization system. In sending system, the spread spectrum modulation and carrier modulation have been mainly realized. In receiving system, using the homodyne receiver, the author has completed the design of carrier demodulation and despreading design. In sequence synchronization system, the capture of pseudo random sequence is completed by using digital matched filter method, and the capture confirmed circuit is designed; the synchronous tracking is completed by using advanced-lag delay locked loop. Modelsim6.5a simulation tools have been used to make unit module simulation and system simulation after the design of each module. After simulation, the design of the DS communication system has been downloaded to the Xilinx’s Spartan-3E XC3S500E chip to make test. The software and hardware of the test results are analyzed, and the realization of the sequences synchronization has been predominantly researched and analysed.Simulation and test results show that:the design of the DS communication system can accurately realize signal send, capture and tracking of the spreading sequence and demodulation of the received data. Each unit module and the whole system software simulation results are correct, the system hardware test results and system simulation results are consistent.