Research On Synchronization Technology Of Pseudo-code In DSSS Communication

Spread spectrum communication is a new type of communication system whichbased on information theory of Shannon. It has series of advantages such as stronganti-interference ability, low probability of intercept, code-division multiple access,signal hidden and so on, and it is used more and more in the communication. As thefirst step of signal processing at the receiver, synchronization plays a vital role inspread spectrum communication. Synchronization of Pseudo-code is the key problemof implementation of the effective transmission of signals in DSSS. Only with this stepcompleted, one can assure receiving data correctly, and then starts the signalprocessing.This paper researched on the synchronization of Pseudo-code in DSSS in anair-ground telemetry and telecontrol spread spectrum modulation system where theuplink based on2DPSK. Focused on the Pseudo-code acquisition and track. Firstcompared the traditional methods of acquisition: sliding correlation, two-way slidingcorrelation, matched filter. Then researched on two improved methods based on thetraditional methods: large step fast acquisition and the improved method of combine ofserial and parallel with auxiliary circuit. Lower the probability of false alarm, and atthe same time shorten the time of acquisition. A Delay-Locked Loop is used in the partof track. The smaller the equivalent noise bandwidth of loop is, the longer the tracktime lasts, and the better the anti-noise performance presents, but the slower it locks.Change the equivalent noise bandwidth of loop into a proper value to ensure thesystem’s performance. The system is simulated with C plus plus and finallyimplemented with FPGA.