Spread Spectrum Communication System Based On Fpga In The Research Of Pn Code Synchronization Technology

Because of the advantages of high spectrum efficiency and strong capabilityof anti-jamming, spread spectrum communication has become a popular tech-nology in the field of information and communication since its birth. In recentyears, with the development of the third generation of mobile communicativetechnology, the future scope of development for the spread spectrumcommunicative technology is broadened. With the advent of the information age,limited frequency resources can not meet the needs of users. The spread spectrumcommunication provides an effective and reasonable solution for the sharing offrequency resources.The premise of direct sequence spread spectrum communication systemworking normally is that the receiver must despread the spread spectrum codecorrectly. But because of the affect of noise and interference as the delay of thechannel and signal, the spreading code phase of sender and receiver can not beinconsistent. Therefore, the receiver should get spreading code synchronizationfirstly. This is the prerequisite of spread spectrum that make sure receiver worksnormally. Code synchronization includes acquisition and tracking. Acquisition isto get the initial synchronization of spreading code phase; there are a certain phasedifferences between receiving code and local code. Tracking will continue toreduce the phase differences to achieve precise synchronization, and maintain thiskind of synchronization in entire communication process.This paper studies the theory of spread spectrum communication for the firsthand. After that, the frequency spectrum of direct sequence spread spectrum signalis analyzed. The characteristics of the longest linear feedback shift register sequence are also studied. Four acquisition methods and two detection judgmentmethods are put forward in this paper. The phase discriminator algorithm and basicparameters of loop filter are given too. This dissertation discusses the loop designmethods in engineering applications. According to the characteristics of spreadspectrum signal, segmented multi-integral sliding correlation method is to bebrought forward. And plus-pulse method is used to achieve sliding acquisition.Second-order digital delay locked loop is designed and implemented. A simplifiedcode tracking loop design method is given too. Finally code synchronizationsystem is implemented in FPGA used software radio technology. The simulationresults and performance analysis is given at last.