通信與電子信息專業(yè)英語 課件 Unit 12 Microwave Communication

Unit12MicrowaveCommunication

12.1microwaveconcepts

12.2MicrowaveCommunicationSystems12.1microwaveconceptsWordsandExpressionsBackgroundsTextWordsandExpressionsvisible adj.看得見的；可見的；顯而易見的visiblelight

可見光(波長400nm-700nm)offset v.抵消；彌補；補償；形成分支 n.偏移量；抵消；補償UHF:UltraHighFrequency 超高頻

NotethatpartsoftheLandSbandsoverlappartoftheUHFband,whichis300to3000MHz.WordsandExpressions5sideband

n.邊帶(頻帶；能帶)Whenacarrierismodulatedbyaninformationsignal,sidebandsareproduced.DSB:DoubleSideBand 雙邊帶SSB:SingleSideBand 單邊帶VSB:VestigialSideBand殘留邊帶WordsandExpressions6regulate vt.調整；校準；管理；控制Useoftheradio-frequencyspectrumisregulatedbythegovernment.grant

v.授予；同意；承認；認為Insomeareas,newlicensesarenolongerbeinggrantedbecausethespectrumspaceforthatserviceiscompletelyfull.WordsandExpressionsdeviation n.[數]偏差frequencydeviation(Fdev,Δf) 頻偏standarddeviation

(σ,thesquarerootofthevariance) 標準差LimitingthedeviationofFMsignalsalsohelpstoreducebandwidth.

WordsandExpressions8QAM:QuadratureAmplitudeModulation

正交幅度調制QAMtransmitsinformationbychangingboththeamplitudeandphaseofacarrierwave,therebydoublingtheeffectivebandwidth.DigitalQAMsarecommonlyusedinradiocommunicationssystemsrangingfromcellulartechnologytoWi-Fi.WordsandExpressions9spreadspectrum 擴頻ThespreadspectrumisatypeofmodulationwheremodulatedsignalBWismuchlargerthanthebasebandsignalBW.Aspecialcode(pseudonoise)isusedforspectrumspreadingandthesamecodeistobeusedtodespreadthesignalatthereceiver.WordsandExpressions10OFDM:OrthogonalFDM

正交頻分復用

amulti-carriermodulationsystemwheredataaretransmittedasacombinationoforthogonalnarrowbandsignalsknownassubcarriers.WordsandExpressions11VHF:VeryHighFrequency

甚高頻300to3000MHztap

v.開發(fā)；利用；裝龍頭；竊聽；輕拍；輕擊Initially,theVHFandUHFbandsweretapped.Today,mostnewcommunicationservicesareassignedtothemicrowaveandmillimeter-waveregions.最初，VHF和UHF頻段被開發(fā)利用。今天，大多數新的通信服務都工作在微波和毫米波區(qū)域。WordsandExpressionslead n.引線；引腳leadwire,pin,pinoutinductivereactance 感抗,感應電阻Inductivereactanceisthepropertyofaninductivecoilthatresiststhechangeinalternatingcurrent(AC)throughit.resonantcircuit 共振電路usedtorespondselectivelytosignalsofagivenfrequencywhilediscriminatingagainstsignalsofdifferentfrequencies.WordsandExpressions13surface-mounted 表面貼裝；表面安裝；表貼式；貼面的SMT:Surface-mountedTechnology 表面貼裝技術THT:Through-holeTechnology 通孔插件技術BGA:BallGridArray 球柵陣列；球形網格陣列WordsandExpressions14stripline n.微波帶狀線；微帶線；帶狀傳輸線microstrip n.微波傳輸帶；微帶線StriplinesandmicrostripsaretypesofPCBtransmissionlinesinacircuitboardlayout.ThemaindifferencebetweenthesetypesoftracesistheirlocationinthePCB:microstripsareonthesurfacelayer,whilestriplinesareonaninnerlayerbetweentworeferenceplanes.WordsandExpressions15cavityresonator 諧振腔；空腔諧振器metal-walledchambersfittedwithdevicesforadmittingandextractingelectromagneticenergy.Whenbeingusedasfilters,theirprimaryfunctionisassignalseparatorsatspecifiedfrequencies.tunedcircuit 調諧電路；諧振腔themostcommonlyusedfrequencyselectivecircuits.WordsandExpressions16inherent adj.固有的；內在的transittime 渡越時間basetransittime 基區(qū)渡越時間transittimeeffect 渡越時間效應transittimenoise 渡越時間噪聲Transittimenoiseariseswhenthechargecarriersrequirecomparativelymoretimetotravelfromoneendtoanotherwithintheconductor.Thiseffectiscalledtransittimeeffect.WordsandExpressions17klystron

n.極超短波用電子管；

調速管；克萊斯管(1-25GHz)magnetron

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

MMWaveTravelingWaveTubesKlystronTubeWordsandExpressions18line-of-sight

視線ionosphere n.電離層hop

n.跳數；跳躍Microwavesignalspenetratetheionosphere,somultiple-hop

communicationisnotpossible.微波信號穿透電離層，因此無法進行多跳通信。Background19RF/MicrowaveBasicsforEngineersandTechs,/course/rf-microwave-basics-for-engineers-and-techs/TextOutline20IntroductionMicrowaveFrequenciesandBandsBenefitsofMicrowavesDisadvantagesofMicrowavesIntroduction21Microwavesaretheultrahigh,superhigh,andextremelyhighfrequenciesdirectlyabovethelowerfrequencyrangeswheremostradiocommunicationnowtakesplaceandbelowtheopticalfrequenciesthatcoverinfrared,visible,andultravioletlight.微波具有超高、非常高和極高頻率，高于現(xiàn)在大多數無線電通信使用的較低頻率范圍，低于包括紅外、可見光和紫外線的光學頻率。Introduction22Theoutstandingbenefitsforradiocommunicationoftheseextremelyhighfrequenciesandaccompanyingshortwavelengthsmorethanoffsetanyproblemsconnectedwiththeiruse.這些極高頻率和伴隨而來的短波對無線電通信的顯著好處，足以抵消其使用帶來的任何問題。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.信道中心頻率的分配方式使得每個信道中的信號不會重疊和干擾相鄰信道中的信號。BenefitsofMicrowaves25Technologicaladvanceshavehelpedsolvesomeproblemsconnectedwithovercrowding:improvetheselectivityofreceiverssqueezemoresignalsintothesamefrequencyspectrumSSB,PSK,QAM,compressing,multiplexing,spreadspectrum,OFDM…moveintothehigherfrequencyrangesBenefitsofMicrowaves26Upto4,000AMbroadcaststationswith10-kHzbandwidthscouldbeaccommodatedwithinthe40-MHz(1percent)bandwidth.40-MHz(1%)帶寬內可容納多達4000個帶寬為10-kHz的AM廣播電臺。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.另一種解決方案是在微波頻率下使用分布式電路元件，如傳輸線，而不是集總元件。Specialversionsoftransmissionlinesknownasstriplines,microstrips,waveguides,andcavityresonatorsarewidelyusedtoimplementtunedcircuitsandreactances.DisadvantagesofMicrowaves31Anotherseriousproblemistransistortransittime—theamountoftimeittakesforthecurrentcarriers(holesorelectrons)tomovethroughadevice.designingsmallerandsmallermicrowavecomponentsandICsusingspecialmaterialssuchasgalliumarsenide(GaAs),indiumphosphide(InP),andsilicongermanium(SiGe)specialvacuumtubesknownasklystrons,magnetrons,andtraveling-wavetubes,GaNsemiconductortransistorsDisadvantagesofMicrowaves32Anotherproblemisthatmicrowavesignals,asdolightwaves,travelinperfectlystraightlines.Thephysicsofelectromagneticwavesindicatesthattheshorterthewavelengthandthehigherthefrequency,theshorterthetransmissionrangeforagivenpowerorantennagain.電磁波的物理性質表明，波長越短，頻率越高，對于給定的功率或天線增益，其傳輸范圍就越短。12.2MicrowaveCommunicationSystemsWordsandExpressionsBackgroundsText33WordsandExpressionsstage n.級；級數；階段input/outputstage

輸入/輸出級multi-stageamplifiers 多級放大器poweramplification 功放，功率放大器AudioPowerAmplifiers 音頻功放RFPowerAmplifiers 射頻功放

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

聲表面波濾波器ASAWfilterisidealforuseinapplicationsrequiringfiltersfrom10MHzto3GHz.WordsandExpressions36boost v.提高；增加；鼓勵；舉起Oneormoreadditionalpoweramplifiersarethenusedtoboostthesignaltothedesiredpowerlevel.mixer n.混頻器FrequencyMixerisanon-lineardevice.ItisthecoreprocessinRFtechnologyanddesign.WordsandExpressions37synthesizer n.合成器；綜合器Afrequencysynthesizerallowsthedesignertogenerateavarietyofoutputfrequenciesasmultiplesofasinglereferencefrequency.overtone n.倍音；泛音anadditionalresonantcircuitisaddedtotheoscillatorcircuitinordertoamplifytheovertonesignalofthequartz.ifaquartzoscillatesinthefundamentaltoneat20MHz,thethirdovertoneoscillatesat60MHzandthefifthovertoneoscillatesat100MHz.WordsandExpressionsfrequencymultiplier 倍頻器Microwavefrequencymultiplier

usesanonlinearresistiveelementtogenerateharmonicsandabandpassfilterselectstheappropriateharmonicfortheoutput.微波倍頻器使用非線性電阻產生諧波，再用帶通濾波器為輸出選擇合適的諧波。WordsandExpressions39Gunndiode 耿氏二極管；體效應管AGunndiodeisasemiconductordeviceformedbyonlyN-typematerial.Itpossessesnegativeresistancecharacteristicduetowhichthesearewidelyusedinhigh-frequencyapplications,workingasbothanamplifierandanoscillator.WordsandExpressions40DRO:DielectricResonatorOscillator介質振蕩器microwaveoscillatorsthatuseadielectricresonator(DR)asthefrequencystabilizingelement,widelyusedbothinmilitaryandcommercialapplicationstoachievelowphasenoise.bandpass n.帶通ThetunedbandpasscircuitsshowninFigure12.3(b)canbemicrostriptransmissionlineswhentransistorcircuitsareused,orcavityresonatorswhenthespecialmicrowavetubesareused.WordsandExpressions41superheterodyne

n.超外差adj.超外差的IF:IntermediateFrequency 中間頻率Asuperheterodynereceivercontainsacombinationofamplificationwithfrequencymixing,andisbyfarthemostpopulararchitectureforamicrowavereceiver.Itmixesthereceivedsignalfrequencywiththefrequencyofthesignalgeneratedbyalocaloscillatoroutputtingalowerfixedfrequencyalsoknownasintermediatefrequency.WordsandExpressions42LNA:Low-NoiseAmplifier

低噪聲放大器PLL:Phase-LockedLoop

鎖相環(huán)VCO:VoltageControlledOscillator

壓控振蕩器LO:LocalOscillator本地振蕩器frequencydivider

分頻器Atitssimplest,aPLLisaclosed-loopfeedbackcontrolcircuittosynchronizetheoutputoscillatorsignalwithareferencesignal.Aphase-lockedloop(PLL)multiplieristheprimarysignalsourceinmodernmicrowavetransceivers.WordsandExpressions43in-phase(I)signal 同相信號quadrature(Q)signal 正交信號Thebasebandprocessorproducesthedigitalin-phase(I)andquadrature(Q)signalsdefiningthemodulationfromthedatainput.基帶處理器根據輸入數據產生調制的數字同相（I）和正交（Q）信號。WordsandExpressions44LPF:Low-PassFilter 低通濾波器BPF:Band-PassFilter 帶通濾波器up-converting

上變頻；向上轉換down-converting 下變頻；向下轉換spacer n.墊片；隔板；襯墊；撐擋washer n.(螺母等的)墊圈，墊片；襯墊nitrogen n.氮；氮氣WordsandExpressions45half-wavedipoleantenna

半波偶極天線（或稱赫茲天線）one-quarterwavelengthverticalantenna 1/4波垂直天線（或稱馬可尼天線）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.微帶傳輸線被用作調諧電路和阻抗匹配電路，而不是由電感線圈和離散電容器組成調諧電路。Transmitters51Microwavetransmitterusingup-conversionwithamixertoachieveanoutputinthemicrowaverange.Transmitters52Thesynthesizeroutputandamicrowavelocaloscillatorsignalareappliedtothemixer.Themixerthentranslatesthesignaluptothedesiredfinalmicrowavefrequency.Theoutputofthemixeristhedesiredfinalfrequencyatarelativelylowpowerlevel,usuallytensorhundredsofmilliwattsatmost.Linearpoweramplifiersareusedtoboostthesignaltoitsfinalpowerlevel.Transmitters53Aconventionalcrystaloscillatorusingfifth-overtoneVHFcrystalsfollowedbyachainoffrequencymultiplierscanbeusedtodevelopthelocaloscillatorfrequency.使用五倍頻VHF晶體的傳統(tǒng)晶振，后接倍頻器鏈，可用于產生本地振蕩器頻率。Alternatively,oneofseveralspecialmicrowaveoscillatorscouldbeused,e.g.,aGunndiode,amicrowavesemiconductorinacavityresonator,oradielectricresonatoroscillator(DRO).Receivers54Amicrowavereceiver:Microwavereceivers,likelow-frequencyreceivers,arethesuperheterodynetype.Receivers55AmorecommonarchitecturetodayisdirectconversiontransmittersandreceiversusingI/Qmodulatorsanddemodulators,asshowninthisfigure.TransmissionLines56However,coaxialcablehasveryhighattenuationatmicrowavefrequencies,andconventionalcableisunsuitableforcarryingmicrowavesignalsexceptforveryshortruns,usuallyseveralfeetorless.然而，同軸電纜在微波頻率下具有非常高的衰減，傳統(tǒng)電纜不適合傳輸微波信號，除非是非常短的距離，通常是幾英尺或更短。Therearespecialmicrowavecoaxialcablesthatcanbeusedonthelowermicrowavebands.TransmissionLines57Theinsulationbetweentheinnerconductorandtheoutertubingcanbeair;insomecases,agassuchasnitrogenispumpedintothecabletominimizemoisturebuildup,whichcausesexcessivepowerloss.內導體和外管之間的絕緣層可以是空氣；在某些情況下，將氮氣等氣體泵入電纜中以最大程度地減少濕氣積聚，這會導致過多的功率損耗。Athighermicrowavefrequencies,Cbandandupward,aspecialhollowrectangularorcircularpipecalledwaveguideisusedforthetransmissionline.Antennas58Atlowmicrowavefrequencies,standardantennatypes,includingthesimpledipoleandtheone-quarterwavelengthverticalantenna,arestillused.Whileatthehigherfrequencies,specialantennasareneeded.Exercises591.Matchtheterms(1)-(6)withthedefinitionsA-F.(1)frequencysynthesi