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1、Atthisyear'sConsumerElectronicsShowinLasVegas,thebigthemewasthe"Internetofthings"-theideathateverythinginthehumanenvironment,fromkitchenappliancestoindustrialequipment,couldbeequippedwithsensorslandprocessorsthatcanexchangedata,helping2withmaintenanceandthecoordinationsoftas
2、ks.Realizingthatvision,however,requirestransmittersthatarepowerfulenoughtobroadcasttodevicesdozensofyardsawaybutenergy-efficientenoughtolastformonths-oreventoharvestenergyfromheatormechanicalvibrations4."Akeychallengeisdesigningthesecircuitswithextremelylowstandbypower,becau
3、semostofthesedevicesarejustsittingidling,waitingforsomeeventtotriggeracommunication,"explainsAnanthaChandrakasan,theJosephF.andNancyP.KeithleyProfessorinBectricalEngineeringatMIT."Whenifson,youwanttobeasefficientaspossible,andwhenit'soff,youwanttoreallycutofftheoff-statepowe
4、r,theleakagespower."Thisweek,attheInstituteofSectricaland日ectronicsEngineers'InternationalSolid-StateQrcuitsConference,Chandrakasan'sgroupwillpresentanewtransmitterdesignthatreducesoff-stateleakage100-fold.Atthesametime,itprovidesadequatepowerforBluetoothtransmission,orforth
5、eevenlonger-range802.15.4wireless-communicationprotocols."Thetrickisthatweborrowtechniquesthatweusetoreducetheleakagepowerindigitalcircuits,"Chandrakasanexplains.Thebasicelementofadigitalcircuitisatransistor?,inwhichtwoelectricalleadsareconnectedbyasemiconductingmaterial,suc
6、hassilicons.Intheirnativestates,semiconductorslOarenotparticularlygoodconductors.Butinatransistor,thesemiconductor9hasasecondwiresittingontopofit,whichrunsperpendicularlyl1totheelectricalleads.Sendingapositivechargethroughthiswire-knownasthegate-drawselectronstowardit.Thecon
7、centrationofelectronscreatesabridgethatcurrentcancrossbetweentheleads.Butwhilesemiconductorsarenotnaturallyverygoodconductors,neitheraretheyperfectinsulatorsi2.Evenwhennochargeisapplied13tothegate,somecurrentstillleaksacrossthetransistor.It'snotmuch,butovertime,itcanmakeabig
8、differenceinthebatterylifeofadevicethatspendsmostofitstimesittingidle.单词解析表
