專業(yè)外語(yǔ)電磁波傳播第9講.ppt

Lecture9ElectromagneticWavePropagation I TextBackgroundsVocabularyTextTour 英譯漢小作文 Backgrounds 電磁場(chǎng)的典型應(yīng)用 通信 廣播載波的產(chǎn)生 輻射 傳播 接收和傳輸天線和收發(fā)和傳輸設(shè)備的設(shè)計(jì) 射頻信道的分析計(jì)算如 移動(dòng)通信 衛(wèi)星通信 微波中繼通信 無(wú)線接入網(wǎng)無(wú)線局域網(wǎng) 光纖通信 電視廣播等 雷達(dá)探測(cè)與反探測(cè)技術(shù)各種雷達(dá)高性能天線和收發(fā)設(shè)備的設(shè)計(jì) 目標(biāo)識(shí)別 成象隱身設(shè)計(jì) 電磁兼容和抗干擾設(shè)計(jì)電子器件 電路和系統(tǒng)是相互之間干擾最小 其它應(yīng)用舉例 國(guó)防領(lǐng)域 電磁炸彈和電磁炸彈防護(hù)醫(yī)療領(lǐng)域 微波治療食品 微波爐 滅菌商業(yè) 射頻識(shí)別IC卡 衛(wèi)星通信地球站天線系統(tǒng) 極軌衛(wèi)星跟蹤接收天線 衛(wèi)星通信地球站 terrestrialpropagationofelectromagneticwaves陸地傳播的電磁波 Ground WavePropagation地波 沿地球表面空間向外傳播無(wú)線電波 Space WavePropagation空間波 象光線一樣沿直線傳播的無(wú)線電波 又稱為視波 Sky WavePropagation天波 利用電離層的反射來(lái)傳播無(wú)線電波 propagation pr p gei n terrestrialpropagationofelectromagneticwaves陸地傳播的電磁波 opticalpropertiesofradiowaves無(wú)線電波的光學(xué)性質(zhì) refraction折射 波穿過(guò)不同的介質(zhì)的時(shí)候傳播方向會(huì)發(fā)生變化 reflection反射diffraction衍射 又稱為繞射 光線照射到物體邊沿后通過(guò)散射繼續(xù)在空間發(fā)射的現(xiàn)象 interference干涉 頻率相同的兩列波疊加 使某些區(qū)域的振動(dòng)加強(qiáng) 某些區(qū)域的振動(dòng)減弱 而且振動(dòng)加強(qiáng)的區(qū)域和振動(dòng)減弱的區(qū)域相互隔開(kāi) refraction ri fr k n reflection ri flek n interference int fi r ns Interferenceinuse powerlineinterference電力線干擾power supplyinterference電源干擾intermodulationinterference互調(diào)干擾intersymbolinterference符號(hào)間干擾 碼間干擾inversemixtureinterference倒向混頻干擾 Interferenceinuse adjacent channelinterference鄰信道干擾atmosphericinterference天電干擾audiointerference聲頻信號(hào)干擾radiointerference射電干擾 無(wú)線電干擾snowinterference 雪花 干擾 adjacent d eis nt 臨近的 Interferenceinuse mirrorinterference鏡像干擾multipathinterference多徑干擾noiseinterference噪聲干擾backgroundinterference背景干擾imagefrequencyinterference像頻干擾 Interferenceinuse harmonicinterference諧波干擾huminterference交流聲干擾broadbandinterference寬帶干擾broadcastinterference廣播干擾backdoorinterference后門干擾 Interferenceinuse coloursubcarrierinterference彩色副載波干擾commonmodeinterference共模干擾continuouswaveinterference連續(xù)波干擾crosstalkinterference交叉干擾 串話干擾electromageticinterference電磁干擾beatinterference拍頻干擾 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 參考譯文 Vocabulary destinationn 目的地polarizationn 物 偏振 現(xiàn)象 極化 作用 兩極化 分化polarizev 使 偏振 使 極化 使 兩極分化planeelectromagneticwave平面電磁波orientationn 方向 方位vectorn 數(shù) 向量 矢量 帶菌者 Vocabulary horizonn 地平 線 知識(shí) 思想等的 范圍 視野paralleladj 平行的 類似的 并聯(lián)的n 平行線 類似 相似物v 相應(yīng) 平行perpendicularadj 垂直的 正交的n 垂線rotatev 使 旋轉(zhuǎn)counter clockwise逆時(shí)針?lè)较?InElectroniccommunicationssystems sometimeitisimpracticalorimpossibletointerconnecttwopiecesofequipmentwithaphysicalfacilitysuchasametallicwireorcable Thisisespeciallytruewhentheequipmentisseparatedbylargespanofwater ruggedmountains orharshdesertterrain orwhencommunicatingwithsatellitetranspondersorbiting22 000milesaboveEarth Also whenthetransmittersandreceiversaremobile aswithtwo wayradiocommunicationsandmobiletelephone providingconnectionswithmetallicfacilitiesisimpossible Therefore freespaceorEarth satmosphereisoftenusedasatransmissionmedium Paragraph2 Vocabulary Facilityn 設(shè)備 f siliti ruggedadj 高低不平的harshadj 粗糙的 荒蕪的terrainn 地形transpondern 衛(wèi)星轉(zhuǎn)發(fā)器 r gid tr n sp nd 參考譯文 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 損失 遺失 喪失dielectricadj 絕緣的dissipatev 消散 disipeit v kju m daii lektrik Radiowavesareelectromagneticwavesand likelight propagatethroughfreespaceinstraightlinewithavelocityof300000000meterspersecond Otherformsofelectromagneticwavesincludeinfrared ultraviolet Xrays andgammarays TopropagateradiowavesthroughEarth satmosphere itisnecessarythattheenergyberadiatedfromthesource thentheenergymustbecapturedatthereceiveend Radiatingandc