专业外语电磁波传播第9讲.pptVIP

Lecture9ElectromagneticWavePropagation I TextBackgroundsVocabularyTextTour 英译汉小作文 Backgrounds 电磁场的典型应用 通信 广播载波的产生 辐射 传播 接收和传输天线和收发和传输设备的设计 射频信道的分析计算如 移动通信 卫星通信 微波中继通信 无线接入网无线局域网 光纤通信 电视广播等 雷达探测与反探测技术各种雷达高性能天线和收发设备的设计 目标识别 成象隐身设计 电磁兼容和抗干扰设计电子器件 电路和系统是相互之间干扰最小 其它应用举例 国防领域 电磁炸弹和电磁炸弹防护医疗领域 微波治疗食品 微波炉 灭菌商业 射频识别IC卡 卫星通信地球站天线系统 极轨卫星跟踪接收天线 卫星通信地球站 terrestrialpropagationofelectromagneticwaves陆地传播的电磁波 Ground WavePropagation地波 沿地球表面空间向外传播无线电波 Space WavePropagation空间波 象光线一样沿直线传播的无线电波 又称为视波 Sky WavePropagation天波 利用电离层的反射来传播无线电波 propagation pr p gei n terrestrialpropagationofelectromagneticwaves陆地传播的电磁波 opticalpropertiesofradiowaves无线电波的光学性质 refraction折射 波穿过不同的介质的时候传播方向会发生变化 reflection反射diffraction衍射 又称为绕射 光线照射到物体边沿后通过散射继续在空间发射的现象 interference干涉 频率相同的两列波叠加 使某些区域的振动加强 某些区域的振动减弱 而且振动加强的区域和振动减弱的区域相互隔开 refraction ri fr k n reflection ri flek n interference int fi r ns Interferenceinuse powerlineinterference电力线干扰power supplyinterference电源干扰intermodulationinterference互调干扰intersymbolinterference符号间干扰 码间干扰inversemixtureinterference倒向混频干扰 Interferenceinuse adjacent channelinterference邻信道干扰atmosphericinterference天电干扰audiointerference声频信号干扰radiointerference射电干扰 无线电干扰snowinterference 雪花 干扰 adjacent d eis nt 临近的 Interferenceinuse mirrorinterference镜像干扰multipathinterference多径干扰noiseinterference噪声干扰backgroundinterference背景干扰imagefrequencyinterference像频干扰 Interferenceinuse harmonicinterference谐波干扰huminterference交流声干扰broadbandinterference宽带干扰broadcastinterference广播干扰backdoorinterference后门干扰 Interferenceinuse coloursubcarrierinterference彩色副载波干扰commonmodeinterference共模干扰continuouswaveinterference连续波干扰crosstalkinterference交叉干扰 串话干扰electromageticinterference电磁干扰beatinterference拍频干扰 TextTour 10 1Introduction Anelectromagneticwavecontainsanelectronicfieldandamagneticfieldat90 toeachother ThepolarizationofaplaneelectromagneticwaveissimplytheorientationoftheelectricfieldvectorinrespecttothesurfaceoftheEarth i e lookingatthehorizon Ifthepolarizationremainsconstant itisdescribedaslinearpolarization Horizontalpolarizationandverticalpolarizationaretwoformsoflinearpolarization IftheelectricfieldispropagatingparalleltotheEarth ssurface thewaveissaidtobehorizontallypolarized IftheelectricfieldispropagatingperpendiculartotheEarth ssurface thewaveissaidtobeverticallypolarized Ifthepolarizationvectorrotates360 asthewavesmovesonewavelengththroughspaceandthefieldstrengthisequalatallanglesofpolarization thewaveisdescribedashavingcircularpolarization Whenthefieldstrengthvarieswithchangesinpolarization thisisdescribedasellipticalpolarization Arotatingwavecanturnineitherdirection Ifthevectorrotatesinaclockwisedirection itisright handed andifthevectorrotatesinacounter clockwisedirection itisconsideredleft handed Paragraph1 参考译文 Vocabulary destinationn 目的地polarizationn 物 偏振 现象 极化 作用 两极化 分化polarizev 使 偏振 使 极化 使 两极分化planeelectromagneticwave平面电磁波orientationn 方向 方位vectorn 数 向量 矢量 带菌者 Vocabulary horizonn 地平 线 知识 思想等的 范围 视野paralleladj 平行的 类似的 并联的n 平行线 类似 相似物v 相应 平行perpendicularadj 垂直的 正交的n 垂线rotatev 使 旋转counter clockwise逆时针方向 InElectroniccommunicationssystems sometimeitisimpracticalorimpossibletointerconnecttwopiecesofequipmentwithaphysicalfacilitysuchasametallicwireorcable Thisisespeciallytruewhentheequipmentisseparatedbylargespanofwater ruggedmountains orharshdesertterrain orwhencommunicatingwithsatellitetranspondersorbiting22 000milesaboveEarth Also whenthetransmittersandreceiversaremobile aswithtwo wayradiocommunicationsandmobiletelephone providingconnectionswithmetallicfacilitiesisimpossible Therefore freespaceorEarth satmosphereisoftenusedasatransmissionmedium Paragraph2 Vocabulary Facilityn 设备 f siliti ruggedadj 高低不平的harshadj 粗糙的 荒芜的terrainn 地形transpondern 卫星转发器 r gid tr n sp nd 参考译文 Free spacepropagationofelectromagneticwavesisoftencalledradiofrequency RF propagationorsimplyradiopropagation Althoughfreespaceimpliesavacuum propagationthroughEarth satmosphereisoftenreferredtoasfree spacepropagationandcanoftenbetreatedasjustthat TheprimarydifferencebeingthatEarth satmosphereintroduceslossestothesignalthatarenotencounteredinavacuum Electromagneticwaveswillpropagatethroughanydielectricmaterial includingair Electromagneticwaves however donotpropagatewellthroughlossyconductors suchasseawater becausetheelectricfieldscausecurrentstoflowinthematerialthatrapidlydissipatethewave senergy Paragraph3 Vocabulary vacuumn 真空adj 真空的lossn 损失 遗失 丧失dielectricadj 绝缘的dissipatev 消散 disipeit v kju m daii lektrik Radiowavesareelectromagneticwavesand likelight propagatethroughfreespaceinstraightlinewithavelocityof300000000meterspersecond Otherformsofelectromagneticwavesincludeinfrared ultraviolet Xrays andgammarays TopropagateradiowavesthroughEarth satmosphere itisnecessarythattheenergyberadiatedfromthesource thentheenergymustbecapturedatthereceiveend Radiatingandc