正交码时分多子信道扩谱系统的伪码捕获技术

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

在提高无人机数据链的抗干扰能力优化问题的研究中,无人机信道存在多普勒频移问题。为解决上述问题,提出正交码时分多子信道扩谱系统。新系统与传统混合扩频系统相比,具有较强的抗干扰能力,使子信道伪码的快速捕获达到系统同步。无人机通信链路中,载体动态性引入的多普勒频移对正交码时分多子信道扩谱系统的收子信道伪码捕获造成了较大困难。在高动态多普勒存在的条件下,传统的伪码捕获方法捕获时间较长。针对正交码时分多子信道扩谱系统的特点,提出了一种改进的频域并行搜索算法,解决了高动态环境下多子信道伪码的快速捕获问题。仿真结果表明,改进方法与二维搜索法相比,在相同条件下伪码捕获时间大大缩短,实时性强且简单有效。

In the study of improving anti -jamming ability of UAV （Unmanned Aerial Vehicle） data link, 1 Doppler frequency shift problem exists inUAV channe. A novel anti -jamming draft, named orthogonal code time di- vision 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 dy- namic situation to realize subchannel PN code acquisition in UAV communication link. Traditional PN code acquisi- tion algorithm costs comparatively long time in highly dynamic Doppler shift situation. For orthogonal code multi sub- channels 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 situa- tion. Simulation results show that the proposed scheme has significantly shorter capture time than that of the two di- mensional searching method under the same condition, and the FFT - based acquisition algorithm is simple and effi- cient.