The Research Of DS/FH System Based On FPGA

As a new communication technology,Spread-Spectrum communication has low probability of interception, anti-jamming capability and other advantages. It has widely been used in military and civil communications and many other applications. DS/FH hybrid spread spectrum system combines the Direct-Spread-Spectrum(DSSS) with the Frequency-Hopping-Spread-Spectrum(FHSS)system.a better system performance can be obtained through a simple system structure compared with the single spread spectrum system, so,the research of key technology in DS/FH system and the implement of the system designed in the paper have very important practical significance.This article aims to find a single chip FPGA solution for DS/FH system and put forward the improvement measures to its key technology. It begins with two parts, the sender and the receiver. As for the sender, at one hand, it gives whole solutions to the system and detailed parameters of each submodule; At the other hand, it uses EDA software programming to simulate a transmitter, whose processing gain is27dB and its hopping speed is1000h/s. As for the receive part, at one hand, the article presents the overall solution to the receiver; At the other hand, it analyses the key technology of the receive part deeply,meanwhile, combing previous research achievements,some theory innovation and structure improvement has been made in this article for system synchronization and anti-jamming algorithm:(1)To improve the acquisition performance of direct sequence spread spectrum(DSSS)system under a high dynamic telecommunication circumstance,a novel PN code acquisition system based on all-phase FFT(apFFT) is presented, the doppler frequences are parallel searched during the PN code phase searching time by the apFFT frequence chanels.at the the same time,the All-Phase Time-Shift Phase Difference method is introduced to correct the Rough doppler frequence estimation,results from the first apFFT.theoretical analysis and simulation results prove that compared with the traditional FFT PN code acquisition method, the proposed scheme,has a better Anti-noise performanc,can be suited to the complex high dynamic communication environment.(2) To improve the acquisition performance of DS/FH system, a new method, which combine rapid frequency identification with fast PN code acquisition algorithm is presented, through this acquisition method, the traditional3D DS/FH hybrid signal acquisition is converted to2D acquisition,the process of the scheme is analyzed, by the analysis result,we can get that compared with traditional DS/FH hybrid signal acquisition scheme the mean acquisition time(MAT) of the mentioned scheme is effectively reduced.(3) To improve the anti-jamming performance of DS/FH hybrid system, a new adaptive narrow-band interference rejection method, which based on wavelet packet transform and combined with recursive least squares(RLS) algorithm is presented. Firstly, the interference is well located through wavelet packet decomposition, then it will be rejected by the RLS. by monte carlo simulation analysis we can get that when the DS/FH system work at quasi-static model, the proposed algorithm has strong adaptability and reject narrowband interference ability, the performance is better than the traditional direct zeros method, which is suitable for multi-tone interference complex communication environment.