PN Code Acquisition Technology in Orthogonal Code Time Division Multi Subchannels Spread Spectrum System

In the study of improving anti-jamming ability of UAV(Unmanned Aerial Vehicle) data link,l Doppler frequency shift problem exists inUAV channe.A novel anti-jamming draft,named orthogonal code time division multi subchannels spread spectrum modulation(OC-TDMSCSSM),is proposed to solve the above problem.The new scheme has better anti-jamming performance than traditional blending spread spectrum system,and rapider acquisition of subchannel PN code to achieve the system synchronization.It is difficult for a receiver operating in dynamic situation to realize subchannel PN code acquisition in UAV communication link.Traditional PN code acquisition algorithm costs comparatively long time in highly dynamic Doppler shift situation.For orthogonal code multi subchannels spread spectrum system,a new acquisition mode,called modified FFT-based parallel searching algorithm,was presented.The algorithm solves the problem of signal acquisition when the receiver operating in dynamic situation.Simulation results show that the proposed scheme has significantly shorter capture time than that of the two dimensional searching method under the same condition,and the FFT-based acquisition algorithm is simple and efficient.