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沈阳理工大学学士学位论文I摘要扩频通信作为一种新型的通信体制，具有很多独特的优点，在军用和民用领域中都得到了广泛的应用。扩频通信中一个关键性的问题就是扩频信号的同步，包括捕获和跟踪两个步骤，同步性能的优劣直接影响到整个扩频通信系统的性能。因此，对直扩系统同步的研究具有很大的实用价值。本文深入研究了扩频通信中直接扩频系统的同步技术，包括伪随机(PN)序列的捕获、跟踪和载波同步。在伪随机(PN)序列的捕获中研究了串并结合的大步进方法。研究了伪码串行-载波并行、伪码并行-载波串行、伪码串行-载波并行、伪码并行-载波并行4种捕获方法。在特定的参数下，设计出直扩通信系统，并在高斯信道条件下，仿真得出了直扩系统的误码率性能曲线，在此基础上运用了伪码并行-载波串行的方法进行仿真分析，从MATLAB仿真结果可以看出捕获方案确实可行。关键词：扩频通信；同步；捕获；跟踪沈阳理工大学学士学位论文IIAbstractAsanewtypeofcommunicationssystem,spreadspectrumcommunicationshasmanyuniqueadvantages,andhasbeenwidelyusedinbothmilitaryandcivilianfields.Thesynchronizationofspreadspecturnsignal,includingacquisitionandtracking,isthekeyproblemofspreadspecturncommunication.Theperformanceofsynchronizinghasdirectimpactonthewholespreadspectruncommunicationsystem.Asaresult,it’sveryimportanttodiscussthisproblem.Thispaperresearchesintosynchronizationtechniquesofdirect-sequencespreadspectrumsystems,whichincludePNcodeacquisition,PNcodetrackingandcarrierrecovery.westudiedPNacquisitionscheme,largestepacquisionscheme.ThispaperdiscussesfourcapturemethodsaboutserialPNcode,serialcarrier,parallelPNcode,serialcarrier,serialPNcode,parallelcarrier,andparallelPNcode,parallelcarrier.Incertainparameters,designofdirectsequencespreadspectrumcommunicationsystem,andintheGausschannelconditions,simulationofthecurveoftheBERperformanceofDSSSsystem,onthebasisofusingtheparallelPNcode,carrierserialsimulation,simulationresultscanbeseenfromtheMATLABcaptureschemeisfeasible.Keywords:SpreadSpectrumCommunications;Synchronization;Acquisition;Tracking沈阳理工大学学士学位论文III目录1绪论............................................................................................................................12直接序列扩频通信的理论基础..................................................................................42.1扩频通信的理论基础.......................................................................................42.1.1基本理论................................................................................................42.1.2扩频通信的特点....................................................................................52.2直接序列扩频通信系统...................................................................................62.3伪随机序列.......................................................................................................92.3.1m序列..................................................................................................103直接序列扩频系统的同步........................................................................................123.1同步机理.........................................................................................................123.2信号捕获.........................................................................................................123.3信号跟踪.........................................................................................................173.3.1载波跟踪技术......................................................................................173.3.2锁相环原理..........................................................................................183.3.3锁频环原理..........................................................................................203.3.4锁相环与锁频环的性能比较..............................................................214直扩系统的仿真分析................................................................................................234.1设计参数.........................................................................................................234.2直扩通信系统的原理框图.............................................................................234.3直扩通信系统的仿真分析.............................................................................244.4直扩系统的抗干扰性能分析.........................................................................305同步仿真分析............................................................................................................315.1同步参数设计.................................................................................................315.2PN码的自相关性仿真...................................................................................315.3捕获.................................................................................................................325.4跟踪.................................................................................................................36结论................................................................................................................................39致谢................................................................................................................................40沈阳理工大学学士学位论文IV参考文献..........................................................................................................................41附录A英文原文..........................................................................................................43附录B中文翻译..........................................................................................................55附录C程序................................................................................................