电子信息与通信工程专业英语译文及习题答案

I.TranslatethefollowingphrasesintounguidedbasiccommunicationsmessageoriginlaserdiodemessageoutputmicrowaveI.Translatethefollowingphrasesintounguidedbasiccommunicationsmessageoriginlaserdiodemessageoutputmicrowaverelaylinkselectricalmessagecarriersourcebit-errorphysicalanalogsignalelectronicsignalprocessorII.Choosethebestanswerintotheblankaccordingtothe1.Abasiccommunicationssystemconsistsofatransmitter,areceiver,.A.aninformationC.anunguidedB.aguidedD.afiberQuiteoftenitisatransducerthatconvertsmessageintoanA.C.nonelectricalOpticalB.D.thepowerlevelsofweaksignals.Theyareneededverylonglinks(hundredsandthousandsofkilometers)toprovidesufficientpowertotheA.B.C.D.causedbywaterorchemicalsislesssevereforglassthanforthecopperreplaces.However,watermustnotpenetratetheglass.Forsubmergedapplications,fibersareencapsulatedwithincables,whichprotectthemfromthewater.A.B.C.D.priceshavedecreased,anddesignshaveimprovedtomakesplicingconnectorizationA.OpticalC.Optical-B.OpticalD.OpticalIII.Translatethefollowingsentencesinto1.Informationchannelscanbedividedintotwocategories:unguidedchannel,andguidedchannel.Theatmosphereisanexampleofanunguidedchanneloverwhichwavescanpropagate.Systemsusingatmosphericchannelsincludecommercialradioandtelevisionbroadcastsandmicrowaverelaylinks.Guidedchannelsincludeavarietyofconductingtransmissionstructures.Therearetwo-wireline,coaxialcable,andrectangularwaveguide.Guidedlinesconductingtransmissionstructures.Therearetwo-wireline,coaxialcable,andrectangularwaveguide.Guidedlinescostmoretomanufacture,install,andservicethandoatmosphericchannels.Guidedchannelshavetheadvantagesofprivacy,weatherindependence,andtheabilitytoconveymessageswithin,under,andaroundphysicalstructures.Fiberwaveguideshavetheseadvantagesandothers.Themodulatorhastwomainfunctions.First,itconvertstheelectricalmessageintotheproperformat.Second,itimpressesthissignalontothewavegeneratedbythecarriersource.Twodistinctcategoriesofmodulationformatareanaloganddigital.Ananalogsignaliscontinuousandreproducestheformoftheoriginalmessagequitefaithfully.Forfiberopticsystems,alaserdiode(LD)oralight-emittingdiode(LED)isused.Thesetwodevicescancorrectlybecalledopticoscillators.Ideally,theyprovidestable,single-frequencywaveswithsufficientpowerforlong-distancepropagation.Actuallaserdiodesandlight-emittingdiodesdiffersomewhatfromthisideal.Theyemitarangeoffrequenciesandgenerallyradiateonlyafewmilliwattsofaveragepower.Opticalamplifiersboostthepowerlevelsofweaksignals.Theyareneededinverylonglinks(hundredsandthousandsofkilometers)toprovidesufficientpowertothereceiver.Repeaters(alsoknownasregenerators)convertweakanddistortedopticalsignalstoelectricalonesandthenregeneratetheoriginaldigitalpulsetrainsforfurthertransmission.Repeaterscanbeusedonlyfordigitalsystems;opticalamplifiersaresuitableforbothanaloganddigitalsignals.Fibersandfibercableshaveturnedouttobesurprisinglystrongandflexible.Somefibersaresoslenderthattheydonotbreakwhenwrappedaroundcurvesofonlyafewcentimetersradius.Fibersareoftenstoredandtransportedwhiletightlywrappedaroundspoolshavingthissmallcurvature.Fiberflexibilityisattractiveforinstallationscontainingmanyturnsalongthetransmissionpath.Foralarge-radiusbend,fibersguidelightwithnegligibleloss.IV.AnswerthefollowingquestionsaccordingtotheHowmanypartsdoesabasiccommunicationssystemconsistof?andwhatareInformationchannelscanbedividedintotwocategories,whatarethey?Pleasegiveanexample.ExplainthecharacteristicsofLEDandWhatarethecharacteristicsofopticalWhataretheimportantpropertiesofI.TranslatethefollowingphrasesintoI.TranslatethefollowingphrasesintoII.Choosethebestanswerintotheblankaccordingtothe1.2.3.4.5.III.Translatethefollowingsentencesinto在光纤通信系统中，则使用半导体激光器(laserdiode，LD)或发光二极管(Light-IV.AnswerthefollowingquestionsaccordingtotheAbasiccommunicationssystemconsistsofatransmitter,areceiver,andaninformationchannel.Amoredetailed,butstillquitegeneralblockdiagramappears,itcanbedescribeasmessageorigin,modulator,carrierSource,channelcoupler,informationchannel,detector,signalProcessor,messageoutput.Informationchannelscanbedividedintotwocategories:unguidedchannel,andguidedchannel.Theatmosphereisanexampleofanunguidedchanneloverwhichwavescanpropagate.Systemsusingatmosphericchannelsincludecommercialradioandtelevisionbroadcastsandmicrowaverelaylinks.Guidedchannelsincludeavarietyofconductingtransmissionstructures.Therearetwo-wireline,coaxialcable,andrectangularwaveguide.Guidedlinescostmoretomanufacture,install,andservicethandoatmosphericchannels.Guidedchannelshavetheadvantagesofprivacy,weatherindependence,andtheabilitytoconveymessageswithin,under,andaroundphysicalstructures.Fiberwaveguideshavetheseadvantagesandothers.single-frequencywaveswithsufficientpowerforlong-distancepropagation.Actuallaserdiodesandlight-emittingdiodesdiffersomewhatfromthisideal.Theyemitarangeoffrequenciesandgenerallyradiateonlyafewmilliwattsofaveragepower.LEDsandlasertomodulatethem—thatis,toimpresstheinformationontheirradiation.Bothofthesedevicesmadeproportionaltothiscurrent.Fibersandfibercableshaveturnedouttobesurprisinglystrongandflexible.Oneofthemostimportantadvantagesoffibersistheirabilitytocarrylargeamountsofinformationandtodosoineitherdigitaloranalogform.Opticfibers,glassorplastic,areinsulators.Fibershaveexcellentrejectionofradio-frequencyinterference(RFI)andofelectromagneticinterference(EMI).Becausefibersareinsulators,theywillnotpickuporpropagateelectromagneticpulses(EMP)causedbynuclearexplosions,whichcaninducemillionsofvoltsinaconductingtransmissionline.Fibersofferadegreeofsecurityandprivacy.Glassfibersthemselvescanwithstandextremetemperaturesbeforedeteriorating.Fibersareavailableinlonglengths,reducingtheneedforsplices.Fairnessrequiresthatsomethingbenotedaboutthedisadvantagesofopticfibers.Easeofmaintenanceandrepairmightbeaconcern.Itiseasiertorepaircopperlinesthanfiber.Moretechnicianshavele