電子信息工程專業(yè)英語教程（第6版） 試卷A

PAGEPagePAGE2ofNUMPAGES4TechnicalEnglishTestforElectronicInformationEngineeringCollege/Department____________Class___________Name____________Section123TotalScoreSECTION1Fillintheblankswithproperterms(30minutes).1真值表6基帶信號2信噪比7尋址模式3采樣保持電路8色度信號4混疊9軟件無線電5時隙10聲卡11DAC16CCD12CPU17PCB13RTOS18AWG14DFT19RISC15LCD20DMMSECTION2TranslatethefollowingpassagesintoChinese(40minutes).Digitalsignalprocessingtaskscanbeperformedbyallprocessors.Specializeddigitalsignalprocessors(DSPs),however,performthesetasksmostefficientlyandmostquickly.WhiletraditionalprocessorsfollowtheVonNeumannarchitecturemodel,whichassumesasharedsinglememorytobeusedforbothprograminstructionsanddata,DSPsusetheHarvardormodifiedHarvardarchitecture,whichincludesmultipleprogramanddatamemories,alongwithmultiplebusestoaccessthem.ThebasicservicesthattheIMT-2000networkissupposedtoprovidetoitsusersare:1.High-qualityvoicetransmission.2.Messaging(replacinge-mail,fax,SMS,chat,etc.).3.Multimedia(playingmusic,viewingvideos,films,television,etc.).4.Internetaccess(Websurfing,includingpageswithaudioandvideo).TheimagesensoremployedbymostdigitalcamerasisaCCD.Somelow-endcamerasuseCMOStechnology.WhileCMOSsensorswillalmostcertainlyimproveandbecomemorepopularinthefuture,theyprobablywon'treplaceCCDsensorsinhigher-enddigitalcameras.Makesurethecamerahastherightresolutionforyourneeds.Ifyouaregoingtotakesnapshotsande-mailthemtofriends,thenyoudon'tneedanythingmorethan640x480pixelresolution.Buyingtheresolutionthatyouneedletsyousavemoney(andharddiskspace).Ontheotherhand,ifyouwanttoprintenlargedversionsofyourphotos,you'llneeda2-megapixelor3-megapixelcamera.SECTION3Readthefollowingpassagesandanswerquestions(30minutes).PassageoneCD-qualityaudiorequiresatransmissionbandwidthof1.411Mbps.Clearly,substantialcompressionisneededtomaketransmissionovertheInternetpractical.Forthisreason,variousaudiocompressionalgorithmshavebeendeveloped.ProbablythemostpopularoneisMPEGaudio,whichhasthreelayers(variants),ofwhichMP3(MPEGaudiolayer3)isthemostpowerfulandbestknown.LargeamountsofmusicinMP3formatareavailableontheInternet,notallofitlegal,whichhasresultedinnumerouslawsuitsfromtheartistsandcopyrightowners.MP3belongstotheaudioportionoftheMPEGvideocompressionstandard.Audiocompressioncanbedoneinoneoftwoways.InwaveformcodingthesignalistransformedmathematicallybyaFouriertransformintoitsfrequencycomponents.Theamplitudeofeachcomponentisthenencodedinaminimalway.Thegoalistoreproducethewaveformaccuratelyattheotherendinasfewbitsaspossible.Theotherway,perceptualcoding,exploitscertainflawsinthehumanauditorysystemtoencodeasignalinsuchawaythatitsoundsthesametoahumanlistener,evenifitlooksquitedifferentonanoscilloscope.Perceptualcodingisbasedonthescienceofpsychoacoustics—howpeopleperceivesound.MP3isbasedonperceptualcoding.Thekeypropertyofperceptualcodingisthatsomesoundscanmaskothersounds.Imagineyouarebroadcastingalivefluteconcertonawarmsummerday.Thenallofasudden,acrewofworkmennearbyturnsontheirjackhammersandstarttearingupthestreet.Noonecanhearthefluteanymore.Itssoundshavebeenmaskedbythejackhammers.Fortransmissionpurposes,itisnowsufficienttoencodejustthefrequencybandusedbythejackhammersbecausethelistenerscannothearthefluteanyway.Thisiscalledfrequencymasking—theabilityofaloudsoundinonefrequencybandtohideasoftersoundinanotherfrequencybandthatwouldhavebeenaudibleintheabsenceoftheloudsound.Infact,evenafterthejackhammersstop,theflutewillbeinaudibleforashortperiodoftimebecausetheearturnsdownitsgainwhentheystartandittakesafinitetimetoturnitupagain.Thiseffectiscalledtemporalmasking.Answerthefollowingquestionswithin50words.Q1:Whyisaudiocompressionneeded?Q2:Whatismp3?Q3:Whatdoesthewordpsychoacousticsmean?Q4:Whatistheaimofwaveformcoding?Q5:Whatisperceptualcoding?PassageTwoAlthoughover50yearsold,thestandardtelevisionsignalisstilloneofthemostcommonwaytotransmitanimage.Figure1showshowthetelevisionsignalappearsonanoscilloscope.Thisiscalledcompositevideo,meaningthatthereareverticalandhorizontalsynchronization(sync)pulsesmixedwiththeactualpictureinformation.Thesepulsesareusedinthetelevisionreceivertosynchronizetheverticalandhorizontaldeflectioncircuitstomatchthevideobeingdisplayed.Eachsecondofstandardvideocontains30completeimages,commonlycalledframes.Avideoengineerwouldsaythateachframecontains525lines,thetelevisionjargonforwhatprogrammerscallrows.Thisnumberisalittledeceptivebecauseonly480to486oftheselinescontainvideoinformation;theremaining39to45linesarereservedforsyncpulsestokeepthetelevision'scircuitssynchronizedwiththevideosignal.Determinethefollowingstatementistrue(T)orfalse(F):No.T/FStatementQ6:()Thetermcompositevideoisanaliasofstandardtelevisionsignal.Q7:()Therearemorethanonemethodsfo