活頁式教材微課版電子信息專業(yè)英語行業(yè)PPT模板/hangye/Chapter6CommunicationSystem通信系統(tǒng)

教學目標6.1★調制與解調：掌握調制作用、信號與載波、模擬信號調制（調幅、調頻、調相）、采樣和編碼、數(shù)字信號調制、解調。★通過調制與解調、通信信道和多路復用、移動電話三篇文章學習通信系統(tǒng)。6.2★通信信道和多路復用：掌握通信信道作用、有線傳輸介質（雙絞線、同軸電纜、光纖）、無線傳輸介質（微波、通信衛(wèi)星）、多路復用作用、頻分復用、時分復用。6.3★移動電話：掌握移動電話功能和使用、移動電話組成、模數(shù)轉化、數(shù)字信號處理、CPU、存儲器、顯示屏。

6.1

Lesson16ModulationandDemodulation

調制與解調NewWordsTechnicalTerms技術詞匯modulationn.調制；調整telecommunicationn.電信；遠程通信impressvt.施加于；給予印象carrierwave載波characteristicsn.特性，特征；特色inaccordancewith依照；與…一致altervt.改變，更改；vi.改變functionn.功能；函數(shù)；vi.運行sinusoidn.正弦曲線parametern.參數(shù)；系數(shù)magnituden.大??；量級；重要amplituden.振幅；豐富，充足termn.術語；學期；vt.叫做phasen.位相；階段；vt.定相suitableadj.適當?shù)?；相配的amplitudemodulation調幅；波幅調制frequencymodulation調頻；頻率調制phasemodulation調相；相位調制TechnicalTerms技術詞匯bandn.波段；樂隊atanyinstant在任何時刻immunityn.免疫力；免除distortionn.變形；失真；扭曲attheexpenseof以…為代價；支付費用bandwidthn.帶寬；頻帶寬度pulse-codemodulation脈沖編碼調制samplevt.取樣；抽樣；n.樣品compactdisc光碟，激光唱片quantizevt.量化；數(shù)字轉換amplitude-shiftkeying幅移鍵控frequency-shiftkeying頻移鍵控phase-shiftkeying相移鍵控finiteadj.有限的；限定的demodulationn.檢波；反調制；解調extractvt.提?。蝗〕鰀etectorn.檢測器；發(fā)現(xiàn)者；偵察器demodulatorn.解調器

6.1

Lesson16ModulationandDemodulation

調制與解調Inelectronicsandtelecommunications,modulationisatechniqueforimpressinginformation(

voice,music,picture,ordata

)onaradio-frequencycarrierwavebyvaryingoneormorecharacteristicsofthewaveinaccordancewiththesignal.Therearevariousformsofmodulation,eachdesignedtoalteraparticularcharacteristicofthecarrierwave.Ifwelookatageneralfunctionforasinusoid:f

(

t

)=Asin(

ωt+φ

).Wecanseethatthissinusoidhas3parametersthatcanbealtered,toaffecttheshapeofthegraph.Thefirstterm,A,iscalledthemagnitude,oramplitudeofthesinusoid.Thenextterm,ωisknownasthefrequency,andthelastterm,φisknownasthephaseangle.All3parameterscanbealteredtotransmitinformation.Thehighfrequencysinusoidalwavethatisusedinthemodulationisknownasthecarrier[4].Itisimportanttonoticethatasimplesinusoidalcarriercontainsnoinformationofitsown.Modulationisusedbecausethesomeinformationsignalsarenotsuitablefordirecttransmission,butthemodulatedsignalmaybemoresuitable.Text

6.1

Lesson16ModulationandDemodulation

調制與解調Inanalogmodulationsystems,varyingtheamplitude,frequency,orphaseofthecarrierresultsinamplitudemodulation(AM),frequencymodulation(FM),orphasemodulation(PM).Amplitudemodulation(AM)isthemodulationmethodusedintheAMradiobroadcastband.Inthissystem，theamplitudeofthecarrierwavevariesinaccordancewiththemodulatingsignal.Infrequencymodulation(FM),thefrequencyofthecarrierwaveisvariedinsuchawaythatthechangeinfrequencyatanyinstantisproportionaltothemodulatingsignal.Itsprincipalapplicationisalsoinradio,whereitoffersincreasednoiseimmunityanddecreaseddistortionovertheAMtransmissionsattheexpenseofgreatlyincreasedbandwidth.TheFMbandhasbecomethechoiceofmusiclistenersbecauseofitslow-noise,wide-bandwidthqualities;itisalsousedfortheaudioportionofatelevisionbroadcast.Phasemodulation,likefrequencymodulation,isaformofanglemodulation(socalledbecausetheangleofthesinewavecarrierischangedbythemodulatingwave).Text

6.1

Lesson16ModulationandDemodulation

調制與解調Inadigitalsignal,theinformationisencodedasasetofdiscretevalues.pulse-codemodulation(PCM)isamethodusedtodigitallyrepresentsampledanalogsignals.PCMhasbeenusedindigitaltelephonesystemsandisalsothestandardformfordigitalaudioincomputersandthecompactdiscformat.IntheFig.6-2diagram,asinewaveissampledandquantizedforpulse-codemodulation.Indigitalmodulation,acarrierwaveismodulatedbyadiscretesignal.Themostfundamentaldigitalmodulationtechniquesareamplitude-shiftkeying(ASK),frequency-shiftkeying(FSK),andphase-shiftkeying(PSK).Theparameterofthecarriersignalisshiftedbythediscreteamplitudesofthedigitalsignal(

Fig.6-3

).Demodulationistheactofextractingtheoriginalinformationsignalfromamodulatedcarrierwave.Eachtypeofmodulationisdifferentandrequiresdifferenttechniquestorecover(demodulate)theinformation.Forexample,forasignalmodulatedwithamplitudemodulation,wecanuseanenvelopedetector.Ontheotherhand,forasignalmodulatedwithanangularmodulation,wemustuseanFMdemodulatororaPMdemodulator.Differentkindsofcircuitsperformthesefunctions.Text

6.1

Lesson16ModulationandDemodulation

調制與解調Figures

Figure6-1Low-frequencyinformationsignal，AMradiowave，F(xiàn)MradiowaveFigure6-3Digitalsignal,ASK,FSK,PSKFigure6-2Samplingandquantizationofasignalfor4-bitPCM

6.1

Lesson16ModulationandDemodulation

調制與解調Ⅰ．Choosethebesttechnicaltermtocompletethefollowingstatements.ExercisesModulationisatechniqueforimpressinginformationonaradio-frequencycarrierwavebyvarying()ofthewaveinaccordancewiththesignal.A.amplitude B.frequency C.phase D.angleThesimplehighfrequencysinusoidalwavewhichcontainsnoinformationofitsownis().A.modulation B.generalfunction C.carrier D.transmission()isthemodulationmethodusedintheradiobroadcastsystem.A.AM B.FM C.PM D.PCMAttheexpenseofgreatlyincreasedbandwidth,()offersincreasednoiseimmunityanddecreaseddistortionintheradiobroadcast.A.amplitudemodulation

B.frequencymodulation C.phasemodulation D.musicmodulation

6.1

Lesson16ModulationandDemodulation

調制與解調Ⅰ．Choosethebesttechnicaltermtocompletethefollowingstatements.ExercisesPCMaudioisahighfidelity,uncompresseddigital()ofananalogaudiosignal.A.encoding B.sampling C.quantizing D.standardformIndigitalmodulation,()arefundamentaldigitalmodulationtechniques.A.PCM B.ASK C.FSK

D.PSK

6.1

Lesson16ModulationandDemodulation

調制與解調Ⅱ．TranslatethefollowingsentencesintoChinese.Exercises1．TheAmplitudeModulated(

AMradio

)carrierfrequenciesareinthefrequencyrange535-1605kHz.Carrierfrequenciesof540to1600kHzareassignedat10kHzintervals.2．TheFMradiobandisfrom88to108MHz.TheFMstationsareassignedcenterfrequenciesat200kHzseparationstartingat88.1MHz,foramaximumof100stations.3．ThesimplestandmostcommonformofASKoperatesasaswitch,usingthepresenceofacarrierwavetoindicateabinaryoneanditsabsencetoindicateabinaryzero.Thistypeofmodulationiscalledon-offkeying.4．Ifthecarrierfrequencybychangingthemethodtosendbinarysymbols,isthefrequencyshiftkeying(

FSK

)method,‘1’whenthereisalowfrequency,‘0’whenthereisahighfrequency.6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用NewWordsTechnicalTerms技術詞匯communicationchannel通信信道transmissionn.播送；傳遞mediumn.介質；媒體median.介質；媒質wiredadj.有線的guidevt.引導；帶領n.指南twistedpairn.雙絞線coaxialcablen.同軸電纜opticalfibern.光纖，光導纖維electromagneticadj.電磁的propagatevt.傳播；傳送interferencen.干擾；干涉dielectricn.電介質metallicadj.金屬的shieldn.防護物；vt.遮蔽electromagneticinterference電磁干擾coren.芯；核心；果心；要點TechnicalTerms技術詞匯capacityn.容量；能力lineofsight視線repeatern.中繼器；轉發(fā)器atintervals相隔一定距離（或時間）relayn.中繼；繼電器；v.轉播historicallyadv.歷史上地；從歷史觀點intercontinentaladj.洲際的；大陸間的telephonyn.電話（學）hand-heldadj.手持的，便攜式的terminaln.終端機uplinkn.上行鏈路downlinkn.下行鏈路multiplexingn.多路技術；v.多重發(fā)訊transmissionrate傳輸速度；傳輸率neighborhoodn.附近；鄰居megahertzn.兆赫kilohertzn.千赫6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用NewWordsTechnicalTerms技術詞匯carrierfrequency載波頻率adjacentstation鄰站；相鄰電臺allowancen.容差；津貼；允許frequency-divisionmultiplexing頻分多路復用allocatevt.分配；vi.指定TechnicalTerms技術詞匯recurringadj.循環(huán)的；重現(xiàn)的segmentn.段；v.分割slotn.（時）隙；狹縫；投硬幣口time-divisionmultiplexing時分多路復用hybridn.混合物；adj.混合的6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Acommunicationchannelisatransmissionmediumthatcarriesasignalbetweenthetransmitterandthereceiver.Transmissionmediaareclassifiedaswiredandwireless.Withwiredtransmissionmedia,thesignalsareguidedalongaphysicalpath,examplesofwiredmediaincludetelephonelines,twistedpaircables,coaxialcables,andopticalfibers.Withwirelesstransmissionmedia,electromagneticwavespropagatethroughtheair.Thetelephonelinesusedtocarrythevoiceanddatacommunicationsconsistofapairinsulatedcopperwires.Thewiresaretwistedaroundeachothertominimizeinterferencefromothertwistedpairsinthecable(Fig.6-4).Twistedpairsaretheleastexpensiveandmostwidelyusedtransmissionmediaforbothanaloganddigitalsignals.Acoaxialcablehasainnerconductorsurroundedbyanon-conductivedielectricinsulatingmaterial(Fig.6-5).Thedielectricissurroundedbymetallicshieldswhichformtheouterconductorandalsoshieldagainstelectromagneticinterference(EMI).Thetermcoaxialcomesfromtheinnerconductorandtheoutershieldsharingthesameaxis.Coaxialcableshavemorebandwidththantwistedpairs.Acoaxialcablecanhandle80timesasmanytelephonetransmissionsastwistedpairmedia.Andmanycomputersinlocalareanetworksarelinkedbycoaxialcables.Text6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Opticalfiberconsistsofacenterglasscoresurroundedbyseverallayersofprotectivematerials(Fig.6-6).Ittransmitslightratherthanelectronicsignalseliminatingtheproblemofelectricalinterference.Opticalfiberhastheabilitytotransmitsignalsovermuchlongerdistancesthancoaxialandtwistedpair.Ithas26,000timesthetransmissioncapacityoftwistedpairmedia.Italsohasthecapabilitytocarryinformationatvastlygreaterspeeds.Microwavetransmissiondiffersfromthepreviouslymentionedcommunicationschannelsinthatsignalistransmittedthroughtheairinsteadofthroughwiresorcables.Microwavetransmissionsoperateathighoperatingfrequenciesof3to10GHz.Thisallowsthemtocarrylargequantitiesofinformationduetothelargebandwidth.Microwavetransmissionislineofsighttransmission.Inordertoovercometheproblemoflineofsightandpoweramplificationofweaksignal,repeatersareusedatintervalsof25to30kilometersbetweenthetransmittingandreceivingend(Fig.6-7).Acommunicationsatelliteisamicrowaverelaystationplacedinouterspace.Insatellitecommunication,microwavesignalistransmittedfromatransmitteronearthtothesatelliteinspace.Thesatelliteamplifiestheweaksignalandtransmitsitbacktothereceiveronearth(Fig.6-8).ThemainadvantageofsatelliteText6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用communicationisthatitisasinglemicrowaverelaystationvisiblefromanypointofaverylargearea.Thefirstandhistoricallymostimportantapplicationforcommunicationsatelliteswasinintercontinentallongdistancetelephony.Theyarealsousedformobileapplicationssuchascommunicationstoships,vehicles,planesandhand-heldterminals,andforTVandradiobroadcasting.Multiplexingisaformofsignaltransmissioninwhichonecommunicationchannelcarriesseveraltransmissionsatthesametime.Thetelephonelinesthatcarryourdailyconversationscancarrythousandsorevenmoreofconversationsatatimeusingmultiplexing.Theexactnumberofsimultaneoustransmissiondependsonthetypeofcommunicationchannelandthedatatransmissionrate.Forexample,oneradiostationcanbroadcastradiowavesintofreespaceatfrequenciesintheneighborhoodof94.5MHz(megahertz)whileanotherradiostationcansimultaneouslybroadcastradiowavesatfrequenciesintheneighborhoodof96.1MHz.Eachradiostationwouldtransmitradiowavesoverafrequencybandwidthofabout180kHz(kilohertz),centeredatfrequenciessuchastheabove,whicharecalledthe‘carrierfrequencies’.Eachstationinthisexampleisseparatedfromitsadjacentstationsby200kHz,andthedifferencebetween200kHzand180kHz(20kHz)isanengineeringallowanceinthecommunicationsystem.Text6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Intheexampleabove,the‘freespacechannel’hasbeendividedintocommunicationschannelsaccordingtofrequencies,andeachchannelisassignedaseparatefrequencybandwidthinwhichtobroadcastradiowaves.Thissystemofdividingthemediumintochannelsaccordingtofrequencyiscalled‘frequency-divisionmultiplexing’(FDM)(Fig.6-9).Anotherwayofdividingacommunicationsmediumintochannelsistoallocateeachsenderarecurringsegmentoftime(a‘timeslot’,forexample,20millisecondsoutofeachsecond),andtoalloweachsendertosendmessagesonlywithinitsowntimeslot.Thismethodofdividingthemediumintocommunicationchannelsiscalled‘time-divisionmultiplexing’(TDM)(Fig.6-10),andisusedinopticalfibercommunication.SomeradiocommunicationsystemsuseTDMwithinanallocatedFDMchannel.Hence,thesesystemsuseahybridofTDMandFDM.Text6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Figures

Figure6-4TwistedpairwiringFigure6-7Microwavetransmission

Figure6-5CoaxialcableFigure6-6Opticalfiber6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Figures

Figure6-8SatellitecommunicationFigure6-9FDMFigure6-10TDM6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Ⅰ．Decidewhetherthefollowingstatementistrueorfalse,andexplainyouranswers.Exercises1．Transmissionmediaincludetelephonelines,twistedpaircables,coaxialcables,opticalfibers,microwavetransmissions,satellitetransmissions,andcellularradiosystems.2．Twistedpairshavefewerbandwidththancoaxialcableoropticalfiber.3．Coaxialcablesareusedtotransmitbothanaloganddigitalsignal.Theyhavesuperiorfrequencycharacteristicscomparedtotwistedpair,andtheycansupporthigherfrequenciesanddatarates.4．Amajoradvantageofopticalfibermediaisnotsusceptibletoelectronicinterference.Therefore,theyareamorereliableformofdatatransmission.5．OpticalFibercablesaresignificantlylessexpensivethancoaxialcable.Adisadvantageofopticalfiberchannelsisthattheycannotcarryinformationovergreatdistances.6．Microwavesarehigh-frequencyradiowavesthatcanonlybedirectedinstraightlines.Consequently,formicrowavetransmissionstobeabletooccuroverlargerdistances,datamessagesmustberelayedfromonelocationtoanotherusingantennasplacedathighaltitudes.6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Ⅰ．Decidewhetherthefollowingstatementistrueorfalse,andexplainyouranswers.Exercises7．Acommunicationsatelliteisusedtolinktwoormoreground-basedmicrowavetransmitters/receivers.Thesatellitereceivestransmissionsononefrequencyband(uplink),amplifiesorrepeatsthesignal,andtransmitsitonanotherfrequency(downlink).8．FDM(

FrequencyDivisionMultiplexing

)andTDM(

TimeDivisionMultiplexing

)aretwomethodsofmultiplexingmultiplesignalsintoasingletransmissionchannel.6.2 Lesson17CommunicationChannelandMultiplexing

通信信道和多路復用Ⅱ．TranslatethefollowingsentencesintoChinese.Exercises1．Thesetwisted-pairinstallationsaregenerallydesignedtosupportvoicetrafficusinganalogsignaling.However,byusingamodem,theycanalsohandledigitaldata.2．Coaxialcableisusedasatransmissionlineforradiofrequencysignals.Itsapplicationsincludefeedlinesconnectingradiotransmittersandreceiverswiththeirantennas,anddistributingcabletelevisionsignals.3．Infiber-opticcommunication,thelightformsanelectromagneticcarrierwavethatismodulatedtocarryinformation.Becauseofitsadvantagesoverelectricaltransmission,opticalfibershavelargelyreplacedcopperwirecommunicationsincorenetworks.4．Communicationssatellitesareofteningeostationaryorbit.Atthehighorbitalaltitudeof35,800kilometers,ageostationarysatelliteorbitstheEarthinthesameamountoftimeittakestheEarthtorevolveonce.5．Inanalogtransmission,signalsarecommonlymultiplexedusingfrequency-divisionmultiplexing(

FDM

),inwhichthecarrierbandwidthisdividedintosubchannelsofdifferentfrequencywidths,eachcarryingasignalatthesametimeinparallel.6．Indigitaltransmission,signalsarecommonlymultiplexedusingtime-divisionmultiplexing(

TDM

),inwhichthemultiplesignalsarecarriedoverthesamechannelinalternatingtimeslots.

6.3

Lesson18MobilePhone

移動電話NewWordsTechnicalTerms技術詞匯mobileadj.移動的；n.移動物體cellphone手機duplexn.雙工basestation基站publictelephone公用電話網(wǎng)networkfixedline固定線路antennan.天線outgoingadj.外出的incomingadj.引入的DSP數(shù)字信號處理器signal-manipulation信號處理choren.家庭雜務；日常零星事務commandv.命令，指揮；n.命令operatingsystem操作系統(tǒng)commitvt.致力于，承諾，從事customizableadj.可定制的TechnicalTerms技術詞匯directoryn.目錄；姓名地址錄rechargevt.再充電；再控告internaladj.內部的；內在的flashmemory閃速存儲器SIMcard用戶識別卡；智能卡service-subscribern.服務訂戶；服務用戶keyn.鑰匙；密鑰；關鍵slidevt.滑動；使滑動featuren.特色，特征；v.特寫built-inadj.嵌入的；n.內置incorporatevt.包含，吸收；合并webbrowser

瀏覽器smartphonen.智能手機resolution

n.[物]分辨率；決議；解決；決心touchscreenn.觸摸屏optimizedadj.最佳化的6.3

Lesson18MobilePhone

移動電話Amobilephone(alsocalledmobileorcellphone)isanelectronicdeviceusedforfullduplextwo-wayradiotelecommunicationsoveracellularnetworkofbasestations(Fig.5-3).Amobilephoneallowsitsusertomakeandreceivetelephonecallstoandfromthepublictelephonenetworkwhichincludesothermobilesandfixedlinephonesacrosstheworld.Cellphonecontainsafewindividualparts:Anamazingcircuitboardcontainingthebrainsofthephone,antenna,aLiquidCrystalDisplay(LCD),akeyboard,amicrophone,aspeakerandabattery(Fig.5-4).Thecircuitboardistheheartofthesystem.HereisonefromatypicalNokiadigitalphone(Fig.5-5,Fig.5-6).Inthephotos,thereareseveralchips.Theanalog-to-digitalanddigital-to-analogconversionchipstranslatetheoutgoingaudiosignalfromanalogtodigitalandtheincomingsignalfromdigitalbacktoanalog.Thedigitalsignalprocessor(DSP)isahighlycustomizedprocessordesignedtoperformsignal-manipulationcalculationsathighspeed.Themicroprocessorhandlesallofthechoresforthekeyboardanddisplay,dealswithcommandandcontrolsignalingwiththebasestationandalsocoordinatestherestofthefunctionsontheboard.Text6.3

Lesson18MobilePhone

移動電話TheROMandFlashmemorychipsprovidestorageforthephone’soperatingsystemandcustomizablefeatures,suchasthephonedirectory.Thepowersectionhandlespowermanagementandrecharging.Finally,theRFamplifiershandlesignalstravelingtoandfromtheantenna.Somephonesstorecertaininformation,ininternalFlashmemory,whileothersuseexternalcardssuchasSIMcard(Fig.5-7).TheSIMstorestheservice-subscriberkeyusedtoidentifyasubscriberonmobiledevice.TheSIMcardmakesiteasytoswitchtoanewphonebysimplyslidingtheSIMoutoftheoldphoneandintothenewone.Thedisplay(Fig.5-8)hasgrownconsiderablyinsizeasthenumberoffeaturesincellphoneshaveincreased.Mostcurrentphonesofferbuilt-inphonedirectories,calculatorsandgames.Andmanyofthephonesincorporatewebbrowser.Asmartphoneisamobilephonebuiltonamobileoperatingsystem.Smartphonestypicallyaddedthefunctionsofpersonaldigitalassistant(PDA)，portablemediaplayers,digitalcameras,andGPSnavigationunitstoformonemulti-usedevice.Modernsmartphonesalsoincludehigh-resolutiontouchscreensandwebbrowsersthatdisplaystandardwebpagesaswellasmobile-optimizedsites.High-speeddataaccessisprovidedbyWi-FiandMobileBroadband.Text6.3

Lesson18MobilePhone

移動電話Figures

Figure5-3Cellularnetwork6.3

Lesson18MobilePhone

移動電話Figures

Figure5-5PCBFront

Figure5-4PartsofacellphoneFigure5-8Display&keypadFigure5-7SIMcardFigure5-6PCBBack6.3

Lesson18MobilePhone

移動電話Ⅰ．Decidewhetherthefollowingstatementistrueorfalse,andexplainyouranswers.Exercises1．Amobilephoneusercanonlymakecallstoothermobilesandonlyreceivetelephonecallsfromthefixedlinephones.2．Mobilephonecontainsabrain,aheart,acircuitboard,anantenna,aLCD,akeyboard,amicrophone,aspeakerandabattery.3．Thereareanalog-to-digitalanddigital-to-analogconversionchips,DSPchip,microprocessorchip,ROMandFlashmemorychips,andotherchipsonthecircuitboa