Direct Sequence Spread Spectrum System In Pseudo-code Synchronization Technology

The spreading spectrum (SS) communication techniques are commonly used in wireless communications, and it is a meaningful thing that we do research on it. Direct sequence spread spectrum technique is the most widely used one and the kernel of the spreading spectrum techniques for people to study. As well as the develop of programmable logic device, using FPGA (Field Programmable GAte)in wireless communication system shows more and more advantages. So researching spreading spectrum techniques based FPGA is a better design choice.Pseudo code is the random sequence which has statistical properties similar to white noise, and it is used as spreading sequence. In the direct sequence spread spectrum system, pseudo code synchronous technique is the key, so this thesis mainly studied the technique. This thesis has given the solution and performance parameters for pseudo code synchronous system, and realized pseudo code synchronous and related modules.The modules in this thesis are as follows:pseudo code generating and information signal spreading spectrum module, and digital down converter module, pseudo code synchronous module, de-spreading spectrum module and so on at the receiving end. The most important module is the pseudo code synchronous module.The process has two parts:capture and track. In the third chapter,this thesis mainly raises the pipeline method for the Digital Match Filter improvement which is used for pseudo code's capture. The improved method uses the idea of pipeline to arrange the parallel capture progress of pseudo code.Simulations prove that the pipeline method reduces hardware resource using, and enhances the capture speed and the system performance. Delay Locked Loop is used for pseudo code's track. The whole pseudo code synchronous system is based on FPGA and the synthesis and simulation results in ISE and Modelsim have proved the correction of the system design.