Fpga Implementation Of Direct Sequence Spread Spectrum Synchronization Technology And Systems

Compared to other communication technologies, Spread Spectrum (SS) technology has the advantages of low probability of intercepting, a high immunity to interference, hiding the useful information and multiple-access communication ability. In modern information times, it has been one of the three high-technological communication means and is developing from military use to commercial environment. In this paper, the author mostly research on Direct Sequence Spread Spectrum (DSSS), the most ordinary one within Spread Spectrum techonologies. However, most of the other research work focuses on theory simulation or implementation using FPGA and DSP, less implementation of a whole Spread Spectrum System only basing on FPGA techonogy.The author of this dissertation alone took on the work of researching and implementing the DSSS System and constructs a whole DSSS simulation platform. In the dissertation, She researches on the key techonology of DSSS System, especially on the most important part —synchronization techonology, including PN sequency acquisition, PN sequency tracking, carrier synchronization and so on. After analysing and comparing all kinds of algorithms of these techonology, the author proposes a whole approach for system rapid and exact synchronization in environment of great carrier frequency offset and low proportion of power of signal and noise. The result of simulation proves that it can synchronize exactly and improves the system performance.Also, the dissertation gives an implementation of a whole DSSS system on software-defined radio platform with FPGA. The author has completed the designing and testing of the whole system including transmitter and receiver in both perfect conditions and unperfect conditions with frequency offset. After testing both the parts and the whole system, the author has successfully implementing the system. This dissertation mostly introduces some research work of the author during the graduate studying.The dissertation is organized as follows:In Chapter 1, first it gives a brief survey of the development of SS and introduces the significance of the research of this dissertation. And, it gives the general work in author's research.In Chapter 2, it researches the theory of DSSS techonology and the advantages of it. This chapter also discusses the characteristics of PN Sequence and the selection of it. At the end of this chapter, the author proposes the implemention chart of both transmitting and receiving systems and introduces all the parts of it.In Chapter 3, basing on the simulation system, it focuses on the research of all the arithmetics of synchronization techonology, including PN sequency acquisition, PN sequency tracking, carrier synchronization and so on. Detailed design arthmetic is analyzed, optimized and simulated. According to all of these, the author proposes a whole approach for system rapid and exact synchronization in conditions of great carrier frequency offset and low proportion of power of signal and noise.Chapter 4, the last chapter, gives the implementation of a whole Spread Spectrum System only basing on FPGA techonogy on software-defined radio platform, as the advanced work of the dissertation. It makes use of the theory and the simulation. The designing of the whole system and the connected testing have completed. Now it is in the last step of the hardware debugging. The system uses the method of blocking designing, which makes it flexible, extensible and compatible.At last, it reviews the contents of the dissertation and according to the limitation of the system designed both in simulation and implementation, some ideas are discussed to improve the future work.