通信工程師考試復(fù)習(xí)題高級(jí)英語(yǔ)試卷

單項(xiàng)選擇題：(Choosethebest Itwas in1969,whentheU.S.DepartmentofDefenseestablishedanationwidenetwork ahandfulofuniversitiesandcontractors.start, B.started,toC.tostart, D.tostart,to(Ifsomebodyelsehadsomethinginteresting ontheircomputer,itwassimplematter aA.stored,to B.tostore,C.storing, D.store,(TheInternetisahuge systems,butitusesjustahandfulof dataA.interconnect, B.interconnected,toC.tointerconnect, D.interconnecting,()4. Themostcommonly asmail.Mailpermitsnetworkusers textualmessagestoeachother.A.use, B.touse,C.used,to D.using,( Todaythousandsofnetworksandmillionsofcomputers theInternet.A.areconnected B.connectedC.to D.connecting()6. Thesimplestway afileonanotherhostistocopyitacrossthenetworktoyour'localhost.FTPcandothis.A. B.toC. D.()7. Oneindicationoftheextentofthisdevelopmentisthetotallengthof whichwasestimated 3.2millionkilometersintheU.S.A.install, B.installing,C.toinstall, D.installed,to()8. Theresearchers producedthefirstcladglassopticalfiberswerenotthinkingof themforcommunications.A.which, B.that,C.who, D.one,to()9. Thesingle-modefiber, inconjunctionwitha1.3μmlaser,providesabandwidthadvantageswhichtranslatesinto repeaterspacingsforhigh-dataratesystems.A,used, B.using,C.use,to D.touse, Intheephonesystem,theuseoffiberopticsfor centralofficeswithinametropolitanareaandforlowerlevelsintheswitchinghierarchyis A:interconnect, B.interconnecting,C.tointerconnect,to D.interconnected,(Thefiberswerefragile,andaway wouldhave A.protect, B.protection,C.toprotect,tobe D.protecting,( ephonesystemwilleventuallybebandwidthsby fiberA.handle, B.handled,C.handling, D.tohandle,(Oneofmanyreasonsfor a ephonesystem itinmanycitiesisthe ephoneA.develop, B.todevelop,toC.develo, D.developed,(The ephonesystemwouldoperatewithina frequencybandandwouldserveanalmost numberofusers A.limited,unlimited, B.limitation,limitation,C.limit,limit, D.limiting,limiting,(LSItechnologyandmassproductioncontributetoreducedcost infutureefamilyshouldbeable ephoneA.which,B.that,C.when,D.sothat,to Microprocessors putersarenow forcontrollingcomplicatedfeaturesandfunctionswithlesspowerandsize previouslypossible.A.used, B.use,C.using, D.usage,()17. OnJan.4,1979,theFCC IllinoisBellephoneCo. developmentalcellularsystemintheChicagoareaandmakealimitedofferingofitscellularservicetothepublic.A.authorize, B.authorizing,C.authorized,to D.toauthorize,()18. Why800MHz?TheFCC'sdecision 800MHzwas ofseverespectrumlimitationsatlowerfrequencybands.A.tochoose, B.choose,toC.choice, D.choice,短語(yǔ)英譯漢：(TranslatethefollowingphrasesintogiantnetworkofcomputerslocatedalloverthebackbonenationwideelectronicremoteliveworldwidesearchingthelargestrepositoryofnetworkfacilitiesthevastmajorityofthecomputersonthetheUnixoperatingtextualawaytomovedatabetweentheinternetandyourtheconvenientsearchingthenetworkedhypertextlongdistancerepeatercommercialopticalfiberthetotallengthofinstalled municationthelow-losssilicafiberswithlossesapproachingtheRaleighroomtemperaturethresholdthelongerwavelengthsubscriberaccessimprovementsincomponentperformanceanddataratesforinstalledfiberopticgigabitpersecondwavelengthwidebandsubscriberloopmultifibreprojectedlightsingle-modedistributed-feedbackinformationswitchingbroadbandfrequencyspectrumthelimitedassignedfrequencycomplicatedfeaturesandlarge-scaleintegratedcircuitdevelopmentalcellularcentralcoordinatingcellularoperationallimitationof ephonelimitedserviceradiocommunicationavailableradiofrequencytheallocatedfrequencytechnologicalseverespectrumFMbroadcastingpropagationpathmultipathradio zone短語(yǔ)漢譯英：(Translatethefollowingphrasesinto

蜂窩式移動(dòng)：(ranslateTheInternetisaninternationalcollectionofcomputernetworksthatallunderstandastandardsystemofaddressesandcommands,connectedtogetherthroughbackbonesystems.Itwasstartedin1969,whentheU.S.DepartmentofDefenseestablishedanationwidenetworktoconnectahandfulofuniversitiesandcontractors.Theoriginalideawastoincreasecomputingcapacitythatcouldsharedbyusersinmanylocations.PeopleontheARPNETquicklydiscoveredthattheycouldexchangemessagesandconductelectronic"conferences"withdistantcolleaguesforpurposesthathadnothingtodowiththemilitaryindustrialcomplex.Ifsomebodyelsehadsomethinginterestingstoredontheircomputer,itwasasimplemattertoobtainacopy.TodaythousandsofnetworksandmillionsofcomputersareconnectedtotheInternet.Itisgrowingsoquicklythatnobodycansayexactlyhowmanyusers"OntheNet".TheInternetisthelargestrepositoryofinformationwhichcanprovideveryverylargenetworkresources.Thenetworkresourcescanbedividedintonetworkfacilitiesresourcesandnetworkinformationresources.Thenetworkfacilitiesresourcesprovideustheabilityofremotecomputationandcommunication.Thenetworkinformationresourcesprovideusallkindsofinformationservices.ThegoalofyouruseoftheInternetisexchangingmessagesorobtaininginformation.WhatyouneedtoknowisthatyoucanexchangemessagewithothercomputersontheInternetanduseyourcomputerasaremoteterminalondistantcomputers.Buttheinternaldetailsofthelinkarelessimportant,aslongasitworks.Themostcommonlyusednetworkserviceiselectronicmail,orsimplyasmail.Mailpermitsnetworkuserstosendtextualmessagestoeachother.Computersandnetworkshandledeliveringthemail,sothatcommunicatingmailusersdonothavetohandledetailsofdelivery,anddonothavetobepresentatthesametimeorce.BeforeyoucanusetheInternet,youmustchooseawaytomovedatabetweentheInternetandyourPC.Thislinkmaybeahigh-speeddatacommunicationcircuit,alocalareanetwork,aephonelineoraradiochannel.Mostlikely,youwilluseaModemattachedtoyour linetotalktotheInternet.Naturally,thequalityofyourInternetconnectionandserviceisdictatedbytheamountofmoneywhichyouarewillingtospend.Althoughalltheseservicescanwellsatisfytheneedsoftheusersforinformationexchange,adefiniterequirementisneededfortheusers.Notonlyshouldtheusersknowwheretheresourceslocate,butalsoheshouldknowsomeoperatingcommandsconcerned.Toeasethesearchingburdenoftheusers,recentlysomeconvenientsearchingtoolsappear,suchasGopher,andWWWNetscape.AsmoreandmoresystemsjointheInternet,andasmoreandmoreformsofinformationcanbeconvertedtodigitalform,theamountofstuffavailabletoInternetuserscontinuestogrow.AtsomepointsverysoonafterthenationwideInternetstartedtogrow,peoplebegantotreattheNetasacommunity,withitsowntraditionandcustoms.WorldWideWeb(WW)isanetworkedhypertextprotocolanduserinterface.Itprovidesaccesstomultipleservicesand slikeGopherdoesbutismoreambitiousinitsmethod.AjumptootherInternetservicecanbetriggeredbyamouseclickona"hotlinked"word,image,oricononthewebpage. municationistherationaleformostofthecurrentinterestinfiberoptics,thiswasnotthecaseduringtheearlydaysofthetechnology.Theresearcherswhoproducedthefirstcladglassopticalfibersintheearly1950swerenotthinkingofusingthemforcommunications;theywantedtomakeimagingbundlesforendoscope.FiberopticswasalreadyawellestablishedcommercialtechnologywhenthefamouspaperbyKaoandHockham,suggestingtheuseoflow-lossopticalfibersforcommunication,appearedin1966.Thefirstlow-losssilicafiberwasdescribedinapublicationwhichappearedinOctoberof1970.Thedateofthispublicationissometimescitedasthebeginningoftheeraoffibercommunication.Althoughthisdevelopmentdidreceiveconsiderableattentionintheresearchcommunityatthetime,itwasfarfrominevitablethatamajorindustrywouldevolve.The20dB/kmlossfigurewasstilltoohighforlong-haul municationsystems.Thefiberwasfragile,andawaytoprotectthemwouldhavetobefound.Therewerenosuitablelightsources.Researchersdidnotknowwhetherfieldterminationandsplicingofopticalcableswouldeverbepractical.Finally,therewereseriousdoubtsastowhetherthesecomponentscouldeverbeproducedeconomicallyenoughforthetechnologytoyamajorroleinthemarketDuringthemiddleandlate1970s,therateofprogresstowardmarketableacceleratedastheemphasisshiftedfromresearchtoengineering.FiberswithlossesapproachingtheRaleighlimitwereproducedinthelaboratory.Microbendlossproblemswere throughtheuseofimprovedfibercoatingsandcablingtechniques.Lightsourcesandimprovedphotodetectorswhichoperatednear1.3μmweredevelopedtotakeadvantageofthelowfiberlossanddispersioninthis"longerwavelengthregion".Dataratesforinstalledfiberopticsystemshaverecentlymovedintothegigabitpersecondrange.Suchsystemsusethespectrallypuredistributed-feed-backlaserstominimizefibertominimumfiberloss,arenowcommonlyusedinlongdistancetransmission.Theuseofwavelengthmultiplexingtofurtherincreasethefiberinformationcapacityis ingmoresystemsandofficesare ingmoreprominent.Intheephonesystem,theuseoffiberopticsusedindemonstrationprojects.Manyobserversbelievethatnationalephonesystemswilleventuallybeupgradedtohandlebandwidthsbyusingfiberoptics.Threecomponentsareinvolvedinabasicopticalfibersystem;thelightsource,thewhichservesastheinformationcarrier,similartoaradiowavesourcesupplyingelectromagneticopticalenergyandconvertsitintoanelectricalform.TheopticalfibertransmissionlineistheOneofmanyreasonsfordeveloa ephonesystemanddeployinginmanycitiesistheoperationallimitationsofconventional ephonesystem;limitedservicecapability,poorserviceperformance,andinefficientfrequencyspectrumutilization.radiofrequencyspectrum.Insettingallocation,theFederalCommunicationsCommissionseekssystemswhichneedminimalbandwidthbutprovidehighusageandconsumerTheideal ephonesystemwouldoperatewithinalimitedassignedfrequencybandandwouldserveanalmostunlimitednumberofusersinunlimitedareas.Threemajorapproachestoachievetheidealare:①Single-sideband,whichdividestheallocatedfrequencybandintoumnumbersof②Cellular,whichreusestheallocatedfrequencybandindifferentgeographicIn1971,thecomputerindustryenteredanewera.Microprocessorsand arenowusedforcontrollingmanycomplicatedfeaturesandfunctionswithlesspowerandsizethanwaspreviouslypossible.Large-scaleintegratedcircuittechnologyreducedthesizeoftransceiverssothattheyeasilyfitintothestandardauto.Theseachievementswereafewoftherequirementsfordeveloadvancedphonesystemsandencouragingengineerstopursuethisdirection.Why800MHz?TheFCC'sdecisiontochoose800MHzwasmadebecauseofseverespectrumlimitationsatlowerfrequencybands.Forexample,FMbroadcastingservicesoperateinthevicinityof100MHz.Theevisionbroadcastingservicestartsat41MHzandextendsto960MHz.Therefore,itwashardfortheFCCtoallocateaspectruminthelowerportionsofthe30to400MHzbandsincetheservicesofthisbandhad esocrowded.Ontheother radiotransmissioncannotbeappliedat10GHzorabovebecauseseverepropagationpathloss,multipathfading,andrainactivitymakethemediumimproperforAbasiccellularsystemconsistsofthreeparts; unit,acellsite,andephoneswitchingoffice.The unitcontainsacontrolunit,atransceiver,andanantennasystem.ThecellsiteprovidesinterfacebetweentheMTSOandthe units.Ithasacontrolunit,radiocabinets,antennas,apowernt,anddataterminals.TheMTSOisthecentralcoordinatingelementforallcellsites,containingthecellularprocessorandcellularswitch.Itinterfaceswithephone zoneoffices,controlscallprocessingandhandlebillingTheradioandhigh-speeddatalinksconnectthethreesubsystemsofthecellularephonesystem.Eachunitcanonlyuseonechannelatatimeforitscommunicationlink.Butthechannelisnotfixed;itcanbeanyoneintheentirebandassignedbytheservingarea,witheachsitehavingmultichannelcapabilitiesthatcanconnectsimultaneouslytoomanyunits.Thecellularswitchswitchescallstoconnectsubscriberstoothersubscribersandtothenationwideephonenetwork.閱讀理解：(ChoosethebestThefirstlow-loss(20dB/km)silicafiberwasdescribedinapublicationwhichappearedOctoberof1970.Thedateofthispublicationissometimescitedasthebeginningoftheeraoffibercommunication.Althoughthisdevelopmentdidreceive4considerableattentionintheresearchcommunityatthetime,itwasfarfrominevitablethatamajorindustrywouldevolve.The20dB/kmlossfigurewasstilltoohighforlong-hall municationsystems.Thefiberswerefragile,andawaytoprotectthemwouldhavetobefound.Therewerenosuitablelightsources.Researcherstherewereseriousdoubtsastowhetherthesecomponentscouldeverbeproduced'economicallyenoughforthetechnologytoyamajorroleinthemarketce.Althoughthetechnologicalbarriersappearedformidable,theeconomicpotentialwasverysignificant.Asaconsequence,researchanddevelopmentactivityexpandedrapidly,andanumberofimportantissueswereresolvedduringtheearly1970s.Duringthemiddleandlate1970s,therateofprogresstowardmarketableproductsacceleratedastheemphasisshiftedfromresearchtoengineering.FiberswithlossesapproachingtheRaleighlimitof2dB/kmatawavelengthof0.8μm,0.3dB/kmat1.3μm,and0.15dB/kmat1.55μm,wereproducedinthelaboratory.Microbendlossproblemswere ethroughtheuseofimprovedfibercoatingsandcablingtechniques.Ruggedcablesandmultifibreconnectorswereproducedforfieldinstallation.Roomtemperaturethresholdcurrentsforcommercialgalliumaluminumarsenidelasersoperatinginthe0.8to0.85μmspectralregionwerereducedtothe20to30mArange,andprojectedlifetimesinthe100000to1000000hourrangewereclaimedforbothlasersandLEDs.Lightsourcesandimprovedphotodetectorswhichoperatednear1.3μmweredevelopedtotakeadvantageofthelowfiberlossanddispersioninthis"longerwavelengthregion".Severalmajorfieldtrialswereundertakenduringthisperiod,includingAT&T'sAtlantaexperimentandChicagoinstallation,andJapan'ssubscriberaccessproject.Improvementsincomponentperformance,cost,andreliabilityby1980$ledtomajorcommitmentsonthepartofephonecompanies.Fibersoonbecamethepreferredtransmissionmediumforlong-haultrunks.Someearlyinstallationsused0.8μmlightsourcesandgraded-indexmultimodefiber,butby1983,designersofintercitylinkswerethinkingintermsof1.3t1m,singlemodesystems.Thesingle-modefiber,usedinconjunctionwitha1.3μLmlaser,providesabandwidthadvantagewhichtranslatesintoincreasedrepeaterspacingsforhighdataratesystems.Dataratesforinstalledfiberopticsystemshaverecentlymovedintogigabitpersecondrange.Suchsystemsusethespectrallypuredistributed-feedbacklaserstominimizefiberdispersioneffects.Fibersdesignedforlowdispersionat1.55μmwavelength,whichcorrespondstominimumfiberloss,arenowcommonlyusedin