超长波透地通信信道建模及弱信号检测算法研究

硕士学位论文超长波透地通信信道建模及弱信号检测算法研究STUDYOFLOWFREQUENCYTHROUGH-THE-EARTHCOMMUNICATIONCHANNELANDWEAKSIGNALDETECTION张君哈尔滨工业大学2012年6月国内图书分类号：TN929.531学校代码：10213国际图书分类号：621.3密级：公开工学硕士学位论文超长波透地通信信道建模及弱信号检测算法研究硕士研究生：张君导师：张中兆教授申请学位：工学硕士学科：信息与通信工程所在单位：电子与信息工程学院答辩日期：2012年7月授予学位单位：哈尔滨工业大学ClassifiedIndex:TNU.D.C:621.3DissertationfortheMasterDegreeinEngineeringSTUDYOFLOW-FREQUENCYTHROUGH-THE-EARTHCOMMUNICATIONCHANNELANDWEAKSIGNALDETECTIONCandidate：JunZhangSupervisor：Prof.ZhongzhaoZhangAcademicDegreeAppliedfor：MasterofEngineeringSpeciality：InformationandCommunicationEngineeringAffiliation：SchoolofElectronicsInformationEngineeringDateofDefence：July.2012Degree-Conferring-Institution：HarbinInstituteofTechnology哈尔滨工业大学工学硕士学位论文摘要透地通信系统在矿业生产中有着异常重要的作用，地面指挥站与矿井下的工作人员之间的沟通联系都需要有透地通信系统的帮助。而有线的透地通信系统的抗损毁能力差，在发生矿井事故时容易瘫痪，对于解救事故造成的井下受困人员起不到什么作用。因此，研究以大地为传输信道的无线透地通信系统是非常有必要的。本文针对大地信道对传输信号衰减严重，接收端信号微弱的问题，做了深入的研究，给出了一些相应的解决办法。本文首先分析了大地的构成以及其作为无线通信信道的特性。在此基础上，通过解析的方法分别推导出把大地视为理想均匀介质和大地三层有耗模型时，电磁波在其中传播的透射系数和反射系数，进而验证了采用低频信号传输才是保证透地通信系统可靠性的重要条件。针对无线透地通信环境复杂，接收端信号弱的问题，本文给出了基于RAKE接收技术的低频振动波透地通信接收方案，考虑地层多径效应的影响以及接收端信噪比的要求，选择时间分集和昀大比值合并的方式来引入分集增益。同时利用matlab/Simulink软件完成了低频振动波透地通信系统的建模与仿真，给出了其误码率性能曲线，并分析了该方案的优缺点。为了解决透地通信系统通信距离有限的困难，本文提出了一种基于匹配滤波的超长波透地通信系统信号接收技术。通过matlab/Simulink对该技术进行建模与仿真，结果表明，在通信传输速率的要求不是很高时，基于匹配滤波的超长波透地系统信号接收技术可以有效的完成地上与地下深处的通信，可靠通信距离可以达到1000米以上。关键词：大地信道；透地通信；超长波；弱信号检测；匹配滤波-I-哈尔滨工业大学工学硕士学位论文AbstractThrough-the-earthcommunicationthatsupportscommunicationbetweentheminingworkersandtheupon-groundofficersplaysavitalroleintheminingindustry.However,themaintenanceofwiredthroughtheearthcommunicationsystemisdifficult.Itisnotefficientinpeoplerescuewhenaccidentoccurs.Therefore,itisnecessarytoinvestigateonthetopicofwirelessthrough-the-earthcommunicationonthechannelofground.Thispapermainlyfocusesontheweaknessofreceivedsignalcausedbytheseriouslyfadingthroughthechannel,andproposesaseriesofsolution.Firstly,thispaperanalyzesthecompositionoftheearthandthesubsequencefeaturesasradiochannel.Supposethattheearthheterogeneous,wederivethethree-layerearthmodel,transmissionandreflectioncoefficientsusinganalyticalmethod.Wealsosubstantiatethatlow-frequencysignalisthekeyofrobustnessofthrough-the-earthcommunication.Secondly,weproposethereceiveschemeoflow-frequencyelasticwavebasedontheRAKEreceivertechnique.Consideringthemulti-patheffectandtherequestofSNR,weusetime-diversityandmaxratiocombiningtogetextragain.Wealsosimulatethelowfrequencytrough-the-earthcommunicationsystemviamatlab/SimulinktoshowtheBERcurvesandanalyzetheadvantagesanddisadvantagesoftheproposedscheme.Finally,areceivemethodusinglow-frequencywavebasedonmatchedfilterisproposedtodealwiththedifficultycausedbythedistance.Throughthesimulationviamatlab/Simulinkwesubstantiatethattheproposedmethodcanaccomplishthecommunicationtaskeffectively.Thereliablefrequencydistancecouldreach1000meters.Keywords:stratummedium,through-the-earthcommunication,low-frequency,weaksignaldetection,matchedfilter-II-哈尔滨工业大学工学硕士学位论文目录摘要.......................................................................................................................I ABSTRACT.............................................................................................................II第1章绪论.........................................................................................................1 1.1研究的背景和意义...................................................................................1 1.2国内外的研究现状...................................................................................2 1.2.1国外透地通信系统的研究进展...............................................................2 1.2.2国内透地通信系统的研究进展...............................................................3 1.3本文结构安排与主要研究内容.................................................................4 第2章透地信道特性研究......................................................................................5 2.1矿井透地通信系统信道特性分析.............................................................5 2.1.1大地媒质的一般结构..............................................................................5 2.1.2大地媒质的电磁参数...............................................................................6 2.2透地信道的衰减特性...............................................................................7 2.3透地通信系统频率的选取........................................................................9 2.4井下无线透地通信信道的干扰.................................................................9 2.4.1透地通信的干扰分析...............................................................................9 2.4.2干扰的抑制方法.....................................................................................10 2.5本章小结................................................................................................12 第3章大地分层模型中电磁波的传播特性分析................................................13 3.1电磁波传播基本理论.............................................................................13 3.1.1电磁波传播的麦克斯韦方程组............................................................13 3.1.2自由空间中的电磁波传播特性分析..................................................