《通信與電子信息科技英語》課件unit 6

ModulationNewwordsandphrases1categorizev.加以類別,分類2broadlyadv.概括地,大致地3amplituden.幅度，幅值，振幅4cosinen.余弦5argumentn.自變量，變元6markedlyadv.顯著地，明顯地7characteristicn.特征，特性8prescribev.指定，規(guī)定9quantizev.量化10parametern.參數(shù),參量Modulation11digitizevt.將……數(shù)字化12proportionaladj.比例的，成比例的

proportionalto與……成比例，成正比13dispersev.分散，散開，擴展14vestigialadj.殘留的,剩余的

vestigialsideband殘留邊帶15integraln.積分；adj.積分的16collectivelyadv.共同地，全體地17representativeadj.典型的,有代表性的18simplificationn.簡化19appreciableadj.可觀的，可評估的20impressv.施加，外加

Modulation21lineofsightn.視線

lineofsightpropagation(電波的)直線傳播22antennan.天線23compactadj.簡潔的，簡明的24treatmentn.論述，分析25fractionaladj.部分的26designationn.指定,指示27complicationn.復(fù)雜化28likewiseadv.同樣地,照樣地29bruteadj.強制的,粗暴的

bruteforcemethod強制法30overwhelmvt.淹沒；覆蓋31contaminationn.污染，雜質(zhì)，污染物

Modulation32transatlanticn.橫渡大西洋的33rupturen.破裂，絕緣擊穿34tradeoffn.折衷,權(quán)衡35tunevt.調(diào)諧36jumblen.混雜37simultaneousadj.同時的；同步的38bankn.組39nonoverlappingadj.不相重疊的40gapn.間隙,間隔41telemetryn.遙測，遙感勘測42stereophonicn.立體聲的

Modulation1carrierwave載波2moreorless差不多，或多或少3cw(continuouswave)連續(xù)波4pulseduration脈沖寬度，脈沖持續(xù)時間5modulatedsignal已調(diào)信號modulatingsignal調(diào)制信號6pulsetrain脈沖序列，脈沖群7roundoff舍入，四舍五入8discretelevel離散電平9amountto等于，實際上是10spectralcomponents頻（光）譜分量

Modulation

11inrelationto關(guān)于,涉及,與……相比12takeon具有，呈現(xiàn)13DM(deltamodulation)δ調(diào)制，增量調(diào)制14ADM(adaptivedeltamodulation)自適應(yīng)增量調(diào)制15DPCM(differentialpulsecodemodulation)差分脈沖編碼調(diào)16ASK(amplitudeshiftkeying)振幅鍵控17FSK(frequencyshiftkeying)移頻鍵控18PSK(phaseshiftkeying)移相鍵控19DPSK(DifferentialPSK)差分相位鍵控20suitto適于，適合于Modulation21electromagneticwave電磁波22electromagneticradiation電磁輻射23.accountfor說明,占,解決,得分24.inaneffortto企圖，努力想25.HartleyShannonlaw哈特萊香農(nóng)定律26.FDM(frequencydivisionmultiplexing)

頻分（多路）復(fù)用27.TDM(timedivisionmultiplexing)時分（多路）復(fù)用28.timeslot時隙29coaxialcable同軸電纜

Modulation

Modulationisaprocessbywhichaninformationsignalf(t)maybeconvertedtoamoreusefulform.Itishelpfultocategorizemodulationbroadlyaccordingtothreebasicmethods.Eachmethodisthensubdividedintovarioustypesofmodulation.CarrierWaveModulationMethodOneofthemostcommonmodulationmethodsistoalteracarrierwaveoftheformAcos(ω0t+θ0),(5.1)whereθ0isanarbitraryconstant,Aisthewavepeakamplitude,andω0isthecarrierfrequency.MoreorlessobviousmodulationapproachesaretomakeAafunctionoftheinformationsignalf(t)ortoaddaphasetermtothecosineargumentwhichdependson

f(t).Thesemethodsmaybecharacterizedascontinuouswave(cw)modulation.Theresultofcwmodulationisusuallyabandpasssignalbecausethecarrierfrequencyisoftenmuchhigherthanthelargestsignificantfrequencycomponentinf(t).

ModulationPulseModulationMethodAnothermodulationmethod,pulsemodulation,involveschangingsomeparameterofatrainofpulses.Forexample,theamplitudeofthepulsescouldbevariedassomefunctionoftheinformationsignalf(t).Alternativeswouldbetovarypulsedurationorposition.Pulsemodulationdoesnotinvolveacarrier.Theresultingmodulatedsignalisstillbasebandbutisnolongertheoriginalinformationsignal.Bothcwandpulsemodulationmaybeclassedasanalogmodulationwhichinvolvesvaryingthemodulatedparametercontinuouslyasalinearfunctionoftheinformationsignal.CodedorDigitalModulationMethodCodedmodulationinvolveschangingacharacteristicofapulsetrainbutis Modulationamarkedlydifferentmethodfrompulsemodulation.Themethodinvolvesfirstsamplingtheinformationsignal,quantizingthesamplebyroundingofftotheclosestofanumberofdiscretelevels,andfinallygeneratingaprescribednumberofpulsesaccordingtoacoderelatedtothenearestdiscretelevel.Inthesimplestsystemthecodemaydeterminethepresenceorabsenceofpulsesintheprescribednumber,or,alternatively,itmaydeterminepulsesign.Bothcasescorrespondtopulseshavingonlytwopossiblelevels.Morecomplicatedsystemsarealsofeasiblewithpulseshavingalargernumberofdiscretelevels.Quantizingandcodingamountstodigitizingthesignal;thus,codedmodulationwillalsobereferredtoasdigitalmodulation.Itisoneofthemostmodernandusefulmethodsofmodulationavailabletoday.

ExercisesⅠ.PleasetranslatethefollowingwordsandphrasesintoChinese.1.AM2.DPSK3.PAM4.PDM5.PPM6.PCM7.DPCM8.ASK9.FSK10.FDM11.TDM12.codedmodulation13.suppressedcarrier14.modulatedsignal

幅度調(diào)制(amplitudemodulation)差分相位鍵控(DifferentialPSK)脈(沖振）幅調(diào)制(pulseamplitudemodulation)脈寬調(diào)制(pulsedurationmodulation)脈（沖相）位調(diào)制(pulsephasemodulation)脈(沖編)碼調(diào)制(pulsecodemodulation)差分脈沖編碼調(diào)制(differentialpulsecodemodulation)振幅鍵控(amplitudeshiftkeying)移頻鍵控(frequencyshiftkeying)頻分（多路）復(fù)用(frequencydivisionmultiplexing)時分（多路）復(fù)用(timedivisionmultiplexing)編碼調(diào)制抑制載波已調(diào)信號ExercisesⅡ.PleasetranslatethefollowingwordsandphrasesintoEnglish.1.帶通信號2.脈沖調(diào)制3.角度調(diào)制4.殘留邊帶抑制載波調(diào)制5.絕對帶寬6.脈沖寬度7.線性函數(shù)8.載波頻率9.模擬調(diào)制10.移相鍵控11.連續(xù)波調(diào)制12.同軸電纜

bandpasssignalpulsemodulationanglemodulationVestigialsidebandsuppressedcarriermodulationabsolutebandwidthpulsedurationlinearfunctioncarrierfrequencyanalogmodulationPSK(phaseshiftkeying)continuouswave(cw)modulationcoaxialcableExercisesⅢ.Fillintheblankswiththemissingword(s).1.Themethodinvolvesfirstsamplingtheinformationsignal,quantizingthesamplebyrounding

off

totheclosestofanumberofdiscretelevels,andfinallygeneratingaprescribednumberofpulsesaccordingtoacoderelatedtothenearestdiscretelevel.2.Codedmodulationwillalsobereferredto

as

digitalmodulation.Itisoneofthemostmodernandusefulmethodsofmodulationavailabletoday.3.InPPMpulsepositionisproportional

to

theamplitudeofthemessagesignal4.Timedivisionmultiplexing(TDM)usespulsemodulationtoputsamplesofdifferentsignals

in

nonoverlappingtimeslots.Forinstance,thegaps

between

pulsescouldbefilledwithsamplesfromothersignals.5.Itisoftennecessarytousemodulationtotranslatetheusefulbandoffrequencies

up

toalargecarrierfrequencysothatefficientelectromagneticradiationispossiblefromanantennahavingreasonablesize.

Exercises6.Thedesignofacommunicationsystemmaybeconstrainedbythecostandavailabilityofhardware,whoseperformanceoftendepends

on

thefrequenciesinvolved7.Fractionalbandwidthconsiderationsaccount

for

thefactthatmodulationunitsarefoundinreceiversaswellasintransmitters.8.Thesemethodsmaybecharacterized

as

continuouswave(cw)modulation.9.Sinceeachstationhasadifferentassignedcarrierfrequency,thedesiredsignalcanbeseparatedfromtheothers

by

filtering.10.PCMmaybeeitherbinary,wherepulseshaveonlytwovoltagelevels,or

μ-ary,wherepulsesmaytake

on

μpossiblelevels.11.Byexploitingthefrequencytranslationproperty

of

cwmodulation,messageinformationcanbeimpressed

on

acarrierwhosefrequencyhasbeenselectedforthedesiredtransmissionmethod.

ExercisesⅣ.Answerthefollowingquestionsaccordingtothetext.1.Whydoesthecwmodulationusuallyresultinabandpasssignal?Theresultofcwmodulationisusuallyabandpasssignalbecausethecarrierfrequencyisoftenmuchhigherthanthelargestsignificantfrequencycomponentinf(t).2.Pleasedescribetheprocedureofthecodedmodulation.Themethodinvolvesfirstsamplingtheinformationsignal,quantizingthesamplebyroundingofftotheclosestofanumberofdiscretelevels,andfinallygeneratingaprescribednumberofpulsesaccordingtoacoderelatedtothenearestdiscretelevel.Exercises3.Whatarethepracticalbenefitsofmodulation?Th