Research On Acquisition Technique Of DS/FH Hybrid Spread Spectrum Signal

DS/FH(Direct Sequence/Frequency Hopping)is a hybrid spread spectrum technolbgy that combines direct sequence spread spectrum and frequency hopping spread spectrum.DS/FH signal more concealed and anti-interference compared with direct sequence signal or frequency hopping signal,so it is widely used in space TT&C system.Acquisition technology is one of the most important technologies in spread spectrum communication,while the core of DS/FH hybrid spread spectrum signal processing technology.Therefore,it is very meaningful to research the acquisition technology of DS/FH hybrid spread spectrum signal.Based on the review of the research status of spread spectrum signal acquisition technology both at home and abroad,the acquisition algorithm of DS/FH hybrid spread spectrum signal is designed and implemented for the characteristics of TT&C signal.The main work is as follows:1.The basic principle of spread spectrum system is expounded.The models of direct sequence spread spectrum,frequency hopping and DS/FH hybrid spread spectrum system are given,and the characteristics of different spread spectrum systems are analyzed;2.In order to avoid the DSSS phase,the hopping frequency and the carrier frequency are separately synchronized,the traditional acquisition algorithm of direct sequence spread spectrum signal and frequency hopping signal are studied,based on this,a signal structure of DS/FH hybrid spread spectrum is designed,in which direct spread code and frequency hopping code are related;3.Aiming at the characteristics of large dynamic and low SNR of TT&C signal,an acquisition algorithm of DS/FH hybrid spread spectrum signal based on PMF_FFT(Partial Matching Filter and Fast Fourier Transform)is proposed.By using MATLAB simulation platform,the algorithm is simulated and expressions of each performance indicators of the algorithm are given;4.The acquisition algorithm of DS/FH hybrid spread spectrum signal proposed in this paper is designed and developed with VHDL programming language on FPGA(Field Programmable Gate Array)hardware platform that can accomplish acquisition of DS/FH hybrid spread spectrum signal;5.The acquisition algorithm of DS/FH hybrid spread spectrum signal based on PMF_FFT is tested by ChipScope logic analyzer.The testing result shows that the acquisition algorithm based on PMF-FFT can acquire DS/FH hybrid spread spectrum signal stably under the conditions that direct rate is 4.5M and frequency hopping rate is 9000Hops/s.