通信与电子信息专业英语 课件 Unit 12 Microwave Communication

Unit12MicrowaveCommunication

12.1microwaveconcepts

12.2MicrowaveCommunicationSystems12.1microwaveconceptsWordsandExpressionsBackgroundsTextWordsandExpressionsvisible adj.看得见的；可见的；显而易见的visiblelight

可见光(波长400nm-700nm)offset v.抵消；弥补；补偿；形成分支 n.偏移量；抵消；补偿UHF:UltraHighFrequency 超高频

NotethatpartsoftheLandSbandsoverlappartoftheUHFband,whichis300to3000MHz.WordsandExpressions5sideband

n.边带(频带；能带)Whenacarrierismodulatedbyaninformationsignal,sidebandsareproduced.DSB:DoubleSideBand 双边带SSB:SingleSideBand 单边带VSB:VestigialSideBand残留边带WordsandExpressions6regulate vt.调整；校准；管理；控制Useoftheradio-frequencyspectrumisregulatedbythegovernment.grant

v.授予；同意；承认；认为Insomeareas,newlicensesarenolongerbeinggrantedbecausethespectrumspaceforthatserviceiscompletelyfull.WordsandExpressionsdeviation n.[数]偏差frequencydeviation(Fdev,Δf) 频偏standarddeviation

(σ,thesquarerootofthevariance) 标准差LimitingthedeviationofFMsignalsalsohelpstoreducebandwidth.

WordsandExpressions8QAM:QuadratureAmplitudeModulation

正交幅度调制QAMtransmitsinformationbychangingboththeamplitudeandphaseofacarrierwave,therebydoublingtheeffectivebandwidth.DigitalQAMsarecommonlyusedinradiocommunicationssystemsrangingfromcellulartechnologytoWi-Fi.WordsandExpressions9spreadspectrum 扩频ThespreadspectrumisatypeofmodulationwheremodulatedsignalBWismuchlargerthanthebasebandsignalBW.Aspecialcode(pseudonoise)isusedforspectrumspreadingandthesamecodeistobeusedtodespreadthesignalatthereceiver.WordsandExpressions10OFDM:OrthogonalFDM

正交频分复用

amulti-carriermodulationsystemwheredataaretransmittedasacombinationoforthogonalnarrowbandsignalsknownassubcarriers.WordsandExpressions11VHF:VeryHighFrequency

甚高频300to3000MHztap

v.开发；利用；装龙头；窃听；轻拍；轻击Initially,theVHFandUHFbandsweretapped.Today,mostnewcommunicationservicesareassignedtothemicrowaveandmillimeter-waveregions.最初，VHF和UHF频段被开发利用。今天，大多数新的通信服务都工作在微波和毫米波区域。WordsandExpressionslead n.引线；引脚leadwire,pin,pinoutinductivereactance 感抗,感应电阻Inductivereactanceisthepropertyofaninductivecoilthatresiststhechangeinalternatingcurrent(AC)throughit.resonantcircuit 共振电路usedtorespondselectivelytosignalsofagivenfrequencywhilediscriminatingagainstsignalsofdifferentfrequencies.WordsandExpressions13surface-mounted 表面贴装；表面安装；表贴式；贴面的SMT:Surface-mountedTechnology 表面贴装技术THT:Through-holeTechnology 通孔插件技术BGA:BallGridArray 球栅阵列；球形网格阵列WordsandExpressions14stripline n.微波带状线；微带线；带状传输线microstrip n.微波传输带；微带线StriplinesandmicrostripsaretypesofPCBtransmissionlinesinacircuitboardlayout.ThemaindifferencebetweenthesetypesoftracesistheirlocationinthePCB:microstripsareonthesurfacelayer,whilestriplinesareonaninnerlayerbetweentworeferenceplanes.WordsandExpressions15cavityresonator 谐振腔；空腔谐振器metal-walledchambersfittedwithdevicesforadmittingandextractingelectromagneticenergy.Whenbeingusedasfilters,theirprimaryfunctionisassignalseparatorsatspecifiedfrequencies.tunedcircuit 调谐电路；谐振腔themostcommonlyusedfrequencyselectivecircuits.WordsandExpressions16inherent adj.固有的；内在的transittime 渡越时间basetransittime 基区渡越时间transittimeeffect 渡越时间效应transittimenoise 渡越时间噪声Transittimenoiseariseswhenthechargecarriersrequirecomparativelymoretimetotravelfromoneendtoanotherwithintheconductor.Thiseffectiscalledtransittimeeffect.WordsandExpressions17klystron

n.极超短波用电子管；

调速管；克莱斯管(1-25GHz)magnetron

n.磁控管(500MHzto12GHz)traveling-wavetube 行波管；行波电子管(300MHzto50GHz)InmanyapplicationssuchasforVSATEarthstations,TVstationsandmilitaryapplicationshighpowerisneededwhichisgeneratedwiththeuseofmicrowavetubes.Thesetubesareusedforamplification,oscillation,switchingandotherapplications.

MMWaveTravelingWaveTubesKlystronTubeWordsandExpressions18line-of-sight

视线ionosphere n.电离层hop

n.跳数；跳跃Microwavesignalspenetratetheionosphere,somultiple-hop

communicationisnotpossible.微波信号穿透电离层，因此无法进行多跳通信。Background19RF/MicrowaveBasicsforEngineersandTechs,/course/rf-microwave-basics-for-engineers-and-techs/TextOutline20IntroductionMicrowaveFrequenciesandBandsBenefitsofMicrowavesDisadvantagesofMicrowavesIntroduction21Microwavesaretheultrahigh,superhigh,andextremelyhighfrequenciesdirectlyabovethelowerfrequencyrangeswheremostradiocommunicationnowtakesplaceandbelowtheopticalfrequenciesthatcoverinfrared,visible,andultravioletlight.微波具有超高、非常高和极高频率，高于现在大多数无线电通信使用的较低频率范围，低于包括红外、可见光和紫外线的光学频率。Introduction22Theoutstandingbenefitsforradiocommunicationoftheseextremelyhighfrequenciesandaccompanyingshortwavelengthsmorethanoffsetanyproblemsconnectedwiththeiruse.这些极高频率和伴随而来的短波对无线电通信的显著好处，足以抵消其使用带来的任何问题。MicrowaveFrequenciesandBands23Themicrowavefrequencyspectrumisdividedupintogroupsoffrequencies,orbands.Recentdevelopmentsinsemiconductortechnology,suchassmaller-geometrysiliconandGaN,havemademillimeterwavespracticalanduseful.BanddesignationFrequencyrangeLband1-2GHzSband2-4GHzCband4-8GHzXband8-12GHzKuband12-18GHzKband18-26.5GHzKaband26.5-40GHzQband30-50GHz

Uband40-60GHzVband50-75GHzEband60-90GHzWband75-110GHzFband90-140GHzDband110-170GHzSubmillimeter>300GHzMillimeterwavesBenefitsofMicrowaves24Theresultingsignal(modulatedsignal)occupiesacertainamountofbandwidth,calledachannel,intheradio-frequency(RF)spectrum.Channelcenterfrequenciesareassignedinsuchawaythatthesignalsusingeachchanneldonotoverlapandinterferewithsignalsinadjacentchannels.信道中心频率的分配方式使得每个信道中的信号不会重叠和干扰相邻信道中的信号。BenefitsofMicrowaves25Technologicaladvanceshavehelpedsolvesomeproblemsconnectedwithovercrowding:improvetheselectivityofreceiverssqueezemoresignalsintothesamefrequencyspectrumSSB,PSK,QAM,compressing,multiplexing,spreadspectrum,OFDM…moveintothehigherfrequencyrangesBenefitsofMicrowaves26Upto4,000AMbroadcaststationswith10-kHzbandwidthscouldbeaccommodatedwithinthe40-MHz(1percent)bandwidth.40-MHz(1%)带宽内可容纳多达4000个带宽为10-kHz的AM广播电台。DisadvantagesofMicrowaves27Thehigherthefrequency,themoredifficultitbecomestoanalyzeelectroniccircuits.Mostcomponentsandcircuitsareanalyzedintermsofelectricandmagneticfields(waveanalysis)atmicrowavefrequencies.Thustechniquescommonlyusedforanalyzingantennasandtransmissionlinescanalsobeusedindesigningmicrowavecircuits.DisadvantagesofMicrowaves28Anotherproblemisthatatmicrowavefrequencies,conventionalcomponentsbecomedifficulttoimplement.Equivalentcircuitsofcomponentsatmicrowavefrequencies.(a)resistor.(b)capacitor.(c)inductor.DisadvantagesofMicrowaves29Tophysicallyrealizeresonantcircuitsatmicrowavefrequencies,thevaluesofinductanceandcapacitancemustbesmallerandsmaller.Tinysurface-mountedchipresistors,capacitors,andinductorshavepartiallysolvedthisproblem.Furthermore,asintegrated-circuitdimensionshavecontinuedtodecrease,smallerandsmalleron-chip

inductorsandcapacitorshavebeenmadesuccessfully.DisadvantagesofMicrowaves30Anothersolutionistousedistributedcircuitelements,suchastransmissionlines,ratherthanlumpedcomponents,atmicrowavefrequencies.另一种解决方案是在微波频率下使用分布式电路元件，如传输线，而不是集总元件。Specialversionsoftransmissionlinesknownasstriplines,microstrips,waveguides,andcavityresonatorsarewidelyusedtoimplementtunedcircuitsandreactances.DisadvantagesofMicrowaves31Anotherseriousproblemistransistortransittime—theamountoftimeittakesforthecurrentcarriers(holesorelectrons)tomovethroughadevice.designingsmallerandsmallermicrowavecomponentsandICsusingspecialmaterialssuchasgalliumarsenide(GaAs),indiumphosphide(InP),andsilicongermanium(SiGe)specialvacuumtubesknownasklystrons,magnetrons,andtraveling-wavetubes,GaNsemiconductortransistorsDisadvantagesofMicrowaves32Anotherproblemisthatmicrowavesignals,asdolightwaves,travelinperfectlystraightlines.Thephysicsofelectromagneticwavesindicatesthattheshorterthewavelengthandthehigherthefrequency,theshorterthetransmissionrangeforagivenpowerorantennagain.电磁波的物理性质表明，波长越短，频率越高，对于给定的功率或天线增益，其传输范围就越短。12.2MicrowaveCommunicationSystemsWordsandExpressionsBackgroundsText33WordsandExpressionsstage n.级；级数；阶段input/outputstage

输入/输出级multi-stageamplifiers 多级放大器poweramplification 功放，功率放大器AudioPowerAmplifiers 音频功放RFPowerAmplifiers 射频功放

DCPowerAmplifiers 直流功放ClassA,B,ABorCWordsandExpressions35SAW:SurfaceAcousticWave Filter

声表面波滤波器ASAWfilterisidealforuseinapplicationsrequiringfiltersfrom10MHzto3GHz.WordsandExpressions36boost v.提高；增加；鼓励；举起Oneormoreadditionalpoweramplifiersarethenusedtoboostthesignaltothedesiredpowerlevel.mixer n.混频器FrequencyMixerisanon-lineardevice.ItisthecoreprocessinRFtechnologyanddesign.WordsandExpressions37synthesizer n.合成器；综合器Afrequencysynthesizerallowsthedesignertogenerateavarietyofoutputfrequenciesasmultiplesofasinglereferencefrequency.overtone n.倍音；泛音anadditionalresonantcircuitisaddedtotheoscillatorcircuitinordertoamplifytheovertonesignalofthequartz.ifaquartzoscillatesinthefundamentaltoneat20MHz,thethirdovertoneoscillatesat60MHzandthefifthovertoneoscillatesat100MHz.WordsandExpressionsfrequencymultiplier 倍频器Microwavefrequencymultiplier

usesanonlinearresistiveelementtogenerateharmonicsandabandpassfilterselectstheappropriateharmonicfortheoutput.微波倍频器使用非线性电阻产生谐波，再用带通滤波器为输出选择合适的谐波。WordsandExpressions39Gunndiode 耿氏二极管；体效应管AGunndiodeisasemiconductordeviceformedbyonlyN-typematerial.Itpossessesnegativeresistancecharacteristicduetowhichthesearewidelyusedinhigh-frequencyapplications,workingasbothanamplifierandanoscillator.WordsandExpressions40DRO:DielectricResonatorOscillator介质振荡器microwaveoscillatorsthatuseadielectricresonator(DR)asthefrequencystabilizingelement,widelyusedbothinmilitaryandcommercialapplicationstoachievelowphasenoise.bandpass n.带通ThetunedbandpasscircuitsshowninFigure12.3(b)canbemicrostriptransmissionlineswhentransistorcircuitsareused,orcavityresonatorswhenthespecialmicrowavetubesareused.WordsandExpressions41superheterodyne

n.超外差adj.超外差的IF:IntermediateFrequency 中间频率Asuperheterodynereceivercontainsacombinationofamplificationwithfrequencymixing,andisbyfarthemostpopulararchitectureforamicrowavereceiver.Itmixesthereceivedsignalfrequencywiththefrequencyofthesignalgeneratedbyalocaloscillatoroutputtingalowerfixedfrequencyalsoknownasintermediatefrequency.WordsandExpressions42LNA:Low-NoiseAmplifier

低噪声放大器PLL:Phase-LockedLoop

锁相环VCO:VoltageControlledOscillator

压控振荡器LO:LocalOscillator本地振荡器frequencydivider

分频器Atitssimplest,aPLLisaclosed-loopfeedbackcontrolcircuittosynchronizetheoutputoscillatorsignalwithareferencesignal.Aphase-lockedloop(PLL)multiplieristheprimarysignalsourceinmodernmicrowavetransceivers.WordsandExpressions43in-phase(I)signal 同相信号quadrature(Q)signal 正交信号Thebasebandprocessorproducesthedigitalin-phase(I)andquadrature(Q)signalsdefiningthemodulationfromthedatainput.基带处理器根据输入数据产生调制的数字同相（I）和正交（Q）信号。WordsandExpressions44LPF:Low-PassFilter 低通滤波器BPF:Band-PassFilter 带通滤波器up-converting

上变频；向上转换down-converting 下变频；向下转换spacer n.垫片；隔板；衬垫；撑挡washer n.(螺母等的)垫圈，垫片；衬垫nitrogen n.氮；氮气WordsandExpressions45half-wavedipoleantenna

半波偶极天线（或称赫兹天线）one-quarterwavelengthverticalantenna 1/4波垂直天线（或称马可尼天线）Atthesefrequencies,antennasizesareverysmall;e.g.,thelengthofahalf-wavedipoleat2GHzisonlyabout3in.Aone-quarterwavelengthverticalantennaforthecenteroftheCbandisonlyabout0.6inlong.Background46Microwaveengineeringandantennas,https:///learn/microwave-antennaTextOutline47IntroductionTransmittersReceiversTransmissionLinesIntroduction48Likeanyothercommunicationsystem,amicrowavecommunicationsystemusestransmitters,receivers,andantennas.Thesamemodulationandmultiplexingtechniquesusedatlowerfrequenciesarealsousedinthemicrowaverange.ButtheRFpartoftheequipmentisphysicallydifferentbecauseofthespecialcircuitsandcomponentsthatareusedtoimplementit.Transmitters49Microwavetransmitterusingfrequencymultiplierstoreachthemicrowavefrequency.Transmitters50Inthelastmultiplierstage,theoperatingfrequencyis1680MHz,wherespecialmicrowavecomponentsandtechniquesmustbeused.Insteadoftunedcircuitsmadeofloopsofwireforinductorsanddiscretecapacitors,microstriptransmissionlinesareusedastunedcircuitsandasimpedance-matchingcircuits.微带传输线被用作调谐电路和阻抗匹配电路，而不是由电感线圈和离散电容器组成调谐电路。Transmitters51Microwavetransmitterusingup-conversionwithamixertoachieveanoutputinthemicrowaverange.Transmitters52Thesynthesizeroutputandamicrowavelocaloscillatorsignalareappliedtothemixer.Themixerthentranslatesthesignaluptothedesiredfinalmicrowavefrequency.Theoutputofthemixeristhedesiredfinalfrequencyatarelativelylowpowerlevel,usuallytensorhundredsofmilliwattsatmost.Linearpoweramplifiersareusedtoboostthesignaltoitsfinalpowerlevel.Transmitters53Aconventionalcrystaloscillatorusingfifth-overtoneVHFcrystalsfollowedbyachainoffrequencymultiplierscanbeusedtodevelopthelocaloscillatorfrequency.使用五倍频VHF晶体的传统晶振，后接倍频器链，可用于产生本地振荡器频率。Alternatively,oneofseveralspecialmicrowaveoscillatorscouldbeused,e.g.,aGunndiode,amicrowavesemiconductorinacavityresonator,oradielectricresonatoroscillator(DRO).Receivers54Amicrowavereceiver:Microwavereceivers,likelow-frequencyreceivers,arethesuperheterodynetype.Receivers55AmorecommonarchitecturetodayisdirectconversiontransmittersandreceiversusingI/Qmodulatorsanddemodulators,asshowninthisfigure.TransmissionLines56However,coaxialcablehasveryhighattenuationatmicrowavefrequencies,andconventionalcableisunsuitableforcarryingmicrowavesignalsexceptforveryshortruns,usuallyseveralfeetorless.然而，同轴电缆在微波频率下具有非常高的衰减，传统电缆不适合传输微波信号，除非是非常短的距离，通常是几英尺或更短。Therearespecialmicrowavecoaxialcablesthatcanbeusedonthelowermicrowavebands.TransmissionLines57Theinsulationbetweentheinnerconductorandtheoutertubingcanbeair;insomecases,agassuchasnitrogenispumpedintothecabletominimizemoisturebuildup,whichcausesexcessivepowerloss.内导体和外管之间的绝缘层可以是空气；在某些情况下，将氮气等气体泵入电缆中以最大程度地减少湿气积聚，这会导致过多的功率损耗。Athighermicrowavefrequencies,Cbandandupward,aspecialhollowrectangularorcircularpipecalledwaveguideisusedforthetransmissionline.Antennas58Atlowmicrowavefrequencies,standardantennatypes,includingthesimpledipoleandtheone-quarterwavelengthverticalantenna,arestillused.Whileatthehigherfrequencies,specialantennasareneeded.Exercises591.Matchtheterms(1)-(6)withthedefinitionsA-F.(1)frequencysynthesi