Research On Synchronization Technology Of Direct Sequence Spread Spectrum Communication

With the development of communication technology, spread spectrum technology demonstrated its doughty strength of life. Especially in the day of electronic countermeasure, it will become the most advanced communication system in military field. Compared with transmitter, spread spectrum receiver maybe has more difficulties in designing, because received signals include a lot of interfering signal. As a result, it's very important and useful to discuss the technology.Direct sequence spread spectrum (DSSS) communication is one of the most common-use technologies in spread spectrum system application. In this dissertation, synchronization, one of key technologies of DSSS communication system, is investigated in the theory and practice. The synchronization technology of DSSS involves in pseudorandom noise (PN) sequence acquisition, PN tracing and carrier wave synchronization. But the PN acquisition is the most difficult technology of them, especially in the case of long sequence rapid acquisition with the communication setting of low signal-to-noise ratio.Firstly, I introduce the basic principle of the DSSS communication system and the correlation characteristics of the m sequence and the Gold sequence respectively. Secondly, PN acquisition technology is investigated deeply. This paper researches and compares three different PN acquisition technologies, namely the single dwell serial PN acquisition system, the multiple dwell serial PN acquisition system and the adaptive threshold PN acquisition system. Then, each system is analyzed in architecture and function. As a result, a new type of PN acquisition project is presented in this paper lastly.Compared with others, the new PN acquisition project adds a delay feedback loop. As it is shown by the theoretical analysis, the new system could increase detection probability and decrease the false alert probability at the same time after each periodicity of correlation operation, which could considerably cut down average time of the PN acquisition and its variance. The experimental result shows that in the case of the lower SNR communication settings, the new system can get better performance than other PN acquisition systems such as the single dwell serial PN acquisition system. Otherwise, the new system's performance is not optimized obviously.