ThehistoryofRFIDWhetherwerealizeitornot,radiofrequencyidentification(RFID)isanintegralpartofourlife.RFIDincreasesproductivityandconvenience.RFIDisusedforhundreds,ifnotthousands,ofapplicationssuchaspreventingtheftofautomobilesandmerchandise；collectingtollswithoutstopping；managingtraffic；gainingentrancetobuildings；automatingparking；controllingaccessofvehiclestogatedcommunities,corporatecampusesandairports；dispensinggoods；providingskiliftaccess；trackinglibrarybooks；buyinghamburgers；andthegrowingopportunitytotrackawealthofassetsinsupplychainmanagement.RFIDtechnologiesisalsobeingpressedintoserviceforuseinU.S.HomelandSecuritywithapplicationssuchassecuringbordercrossingsandintermodalcontainershipmentswhileexpeditinglow-riskactivities.RFIDisatermcoinedforshort-rangeradiotechnologyusedtocommunicatemainlydigitalinformationbetweenastationarylocationandamovableobjectorbetweenmovableobjects.AvarietyofradiofrequenciesandtechniquesareusedinRFIDsystems.RFIDisgenerallycharacterizedbyuseofsimpledevicesononeendofthelinkandmorecomplexdevicesontheotherendofthelink.Thesimpledevices(oftencalledtagsortransponders)aresmallandinexpensive,canbedeployedeconomicallyinverylargenumbers,areattachedtotheobjectstobemanaged,andoperateautomatically.Themorecomplexdevices(oftencalledreaders,interrogators,beacons)aremorecapableandareusuallyconnectedtoahostcomputerornetwork.Radiofrequenciesfrom100kHzto10GHzhavebeenused.ThetagsareusuallybuiltusingCMOScircuitrywhileothertechnologiescanbeusedsuchassurfaceacousticwave(SAW)devicesortunedresonators.Tagscanbepoweredbyabatteryorbyrectificationoftheradiosignalsentbythereader.Tagscansenddatatothereaderbychangingtheloadingofthetagantennainacodedmannerorbygenerating,modulating,andtransmittingaradiosignal.Avarietyofmodulationandcodingtechniqueshavebeenused.RFIDsystemscanbereadonly(dataistransferredonlyinonedirection,fromthetagtothereader)orreadandwrite(two-waycommunication).AtypicalRFIDsystemcanusetheprincipleofmodulatedbackscatter(seeFig.1).InthistypeofRFIDsystem,totransferdatafromthetagtothereader,thereadersendsanun-modulatedsignaltothetag.Thetagreadsitsinternalmemoryofstoreddataandchangestheloadingonthetagantennainacodedmannercorrespondingtothestoreddata.Thesignalreflectedfromthetagisthusmodulatedwiththiscodedinformation.Thismodulatedsignalisreceivedbythereader,demodulatedusingahomodynereceiver,anddecodedandoutputasdigitalinformationthatcontainsthedatastoredinthetag.Tosenddatafromthereadertothetag,thereaderamplitudemodulatesitstransmittedradiosignal.Thismodulatedsignalisreceivedbythetaganddetectedwithadiode.Thedatacanbeusedtocontroloperationofthetag,orthetagcanstorethedata.Asimplediodedetectorallowsthedetectioncircuitryinthetagtobesimpleandconsumelittlepower.Mankindsuseandunderstandingofelectricity,magnetism,andelectromagneticinveryearlytimeswaslimitedtohiseyesight,observationofelectrostaticdischarge(dontstandunderalargetreeduringalightningstorm),andthemagneticpropertiesoflodestones.Earlyapplicationsprobablyincludedmakinglightwithfire,useofmirrorsforsignaling,anduseoflodestonesfornavigation.Scientificunderstandingprogressedveryslowlyuntilaboutthe1600s.Fromthe1600sto1800stherewasanexplosionofobservationalknowledgeofelectricity,magnetism,andopticsaccompaniedbyagrowingbaseofmathematicallyrelatedobservations.The1800smarkedthebeginningofthefundamentalunderstandingofelectromagneticenergy.In1846,EnglishexperimentalistMichaelFaradayproposedthatbothlightandradiowavesareaformofelectromagneticenergy.In1864,ScottishphysicistJamesClerkMaxwellpublishedhistheoryonelectromagnetic.In1887,GermanphysicistHeinrichRudolfHertzconfirmedMaxwellselectromagnetictheoryandproducedandstudiedelectromagneticwaves(radiowaves).Hertziscreditedasthefirsttotransmitandreceiveradiowaves,andhisdemonstrationswerefollowedquicklybyAleksandrPopovinRussia.In1896,GuglielmoMarconidemonstratedthefirstsuccessfultransmissionofradiotelegraphyacrosstheAtlantic,andtheworldwouldneverbethesame.Forwardto20thcenturyIn1906,ErnstF.W.Alexandersondemonstratedthefirstcontinuouswave(CW)radiogenerationandtransmissionofradiosignals.Thisachievementmarksthebeginningofmodernradiocommunication,whereallaspectsofradiowavesarecontrolled.Theearly20thcenturywasconsideredthebirthofradar.TheworkinradarduringWorldWarIIwasassignificantatechnicaldevelopmentastheManhattanProject.Radarsendsoutradiowavesfordetectingandlocatinganobjectbythereflectionoftheradiowaves.Thisreflectioncandeterminethepositionandspeedofanobject.Radarssignificancewasquicklyunderstoodbythemilitary,somanyoftheearlydevelopmentswereshroudedinsecrecy.SinceoneformofRFIDisthecombinationofradiobroadcasttechnologyandradar,itisnotunexpectedthattheconvergenceofthesetworadiodisciplinesandthethoughtsofRFIDoccurredontheheelsofthedevelopmentofradar.GenesisofanideaAnearly,ifnotthefirst,workexploringRFIDisthelandmarkpaperbyHarryStockman,“CommunicationbyMeansofReflectedPower,”publishedin1948.Stockmanstated“Evidently,considerableresearchanddevelopmentworkhastobedonebeforetheremainingbasicproblemsinreflected-powercommunicationaresolved,andbeforethefieldofusefulapplicationsisexplored.”ThirtyyearswouldpassbeforeStockmansvisionwouldreachfruition.Otherdevelopmentswereneeded:thetransistor,theintegratedcircuit,themicroprocessor,developmentofcommunicationnetworks,andchangesinwaysofdoingbusiness.ThesuccessofRFIDwouldhavetowaitawhile.Muchhashappenedinthe57yearssinceStockmanswork.The1950swereaneraofexplorationofRFIDtechniquesfollowingtechnicaldevelopmentsinradioandradarinthe1930sand1940s.SeveraltechnologiesrelatedtoRFIDwerebeingexploredsuchasthelongrangetranspondersystemsof“identification,friend,orfoe”(IFF)foraircraft.Developmentsofthe1950sincludesuchworksasD.B.Harriss“Radiotransmissionsystemswithmodulatablepassiveresponder.”ThewheelsofRFIDdevelopmentwereturning.RFIDbecomesrealityThe1960swerethepreludetotheRFIDexplosionofthe1970s.R.F.HarringtonstudiedtheelectromagnetictheoryrelatedtoRFIDinhispapersincluding“TheoryofLoadedScatterers”in1964.InventorswerebusywithRFID-relatedinventionssuchasRobertRichardsons“Remotelyactivatedradiofrequencypowereddevices,”andJ.H.Vogelmans“Passivedatatransmissiontechniquesutilizingradarechoes.”Commercialactivitieswerebeginninginthe1960s.SensormaticandCheckpointwerefoundedinthelate1960s.Thesecompanies,withotherssuchasKnogo,developedelectronicarticlesurveillance(EAS)equipmenttocounterthetheftofmerchandise.Thesetypesofsystemsareoftenuse1-btags；onlythepresenceorabsenceofatagcouldbedetected,butthetagscouldbemadeinexpensivelyandprovidedeffectiveantitheftmeasures.Thesetypesofsystemsusedeithermicrowave(generationofharmonicsusingasemiconductor)orinductive(resonantcircuits)technology.EASisarguablythefirstandmostwidespreadcommercialuseofRFID.Tagscontainingmultiplebitsweregenerallyexperimentalinnatureandwerebuiltwithdiscretecomponents.Whilesingle-bitEAStagsweresmall,multi-bittagswerethesizeofaloafofbread,constrainedinsizebythedictatesofthecircuitry.Inthe1970sdevelopers,inventors,companies,academicinstitutions,andgovernmentlaboratorieswereactivelyworkingonRFID,andnotableadvanceswerebeingrealizedatresearchlaboratoriesandacademicinstitutionssuchasLosAlamosScientificLaboratory,NorthwesternUniversity,andtheMicrowaveInstituteFoundationinSweden.AnearlyandimportantdevelopmentwastheLosAlamosworkthatwaspresentedbyAlfredKoelle,StevenDepp,andRobertFreyman,“Short-RangeRadio-TelemetryforElectronicIdentificationUsingModulatedBackscatter,”in1975.Thisdevelopmentsignaledthebeginningofpractical,completelypassivetagswithanoperationalrangeoftensofmeters.LargecompanieswerealsodevelopingRFIDtechnology,suchasRaytheonsRaytagin1973andRichardKlenschofRCAdevelopinganelectronicidentificationsystemin1975.ThePortAuthorityofNewYorkandNewJerseywasalsotestingsystemsbuiltbyGeneralElectric,Westinghouse,Philips,andGlenayre.Resultswerefavorable,butthefirstcommerciallysuccessfultransportationapplicationofRFID,electronictollcollection,wasnotyetreadyforprimetime.The1970swerecharacterizedprimarilybydevelopmentalwork.Intendedapplicationswereforanimaltracking,vehicletracking,andfactoryautomation.ExamplesofanimaltaggingeffortswerethemicrowavesystemsatLosAlamosandIdentronixandtheinductivesystemsinEurope.InterestinanimaltaggingwashighinEurope.AlfaLaval,Nedap,andothersweredevelopingRFIDsystems.TransportationeffortsincludedworkatLosAlamosandbytheInternationalBridgeTurnpikeandTunnelAssociation(IBTTA)andtheUnitedStatesFederalHighwayAdministration.Thelattertwosponsoredaconferencein1973thatconcludedtherewasnonationalinterestindevelopingastandardforelectronicvehicleidentification.Thisisanimportantdecisionsinceitwouldpermitavarietyofsystemstodevelop,whichwasgood,becauseRFIDtechnologywasinitsinfancy.Researcheffortscontinuedaswell.R.J.Kingauthoredabookaboutmicrowavehomodynetechniquesin1978.ThisbookisanearlycompendiumoftheoryandpracticeusedinbackscatterRFIDsystems.Tagtechnologyhadimprovedwithreductionsinsizeandimprovementsinfunctionality.Thekeytotheseadvancementswastheuseoflow-voltage,lowpowerCMOSlogiccircuits.Tagmemoryutilizedswitchesorwirebondsandhadimprovedwithuseoffusiblelinkdiodearraysbytheendofthedecade.The1980sbecamethedecadeforfullimplementationofRFIDtechnology,thoughinterestsdevelopedsomewhatdifferentlyinvariouspartsoftheworld.ThegreatestinterestsintheUnitedStateswerefortransportation,personnelaccess,and,toalesserextent,animals.InEurope,thegreatestinterestswereforshort-rangesystemsforanimalsandindustrialandbusinessapplications,thoughtollroadsinItaly,France,Spain,Portugal,andNorwaywereequippedwithRFID.AkeytotherapidexpansionofRFIDapplicationswasthedevelopmentofthepersonalcomputer(PC)thatallowedconvenientandeconomicalcollectionandmanagementofdatafromRFIDsystems.IntheAmericas,theAssociationofAmericanRailroadsandtheContainerHandlingCooperativeProgramwereactivewithRFIDinitiatives.TestsofRFIDforcollectingtollshadbeengoingonformanyyears,andthefirstcommercialapplicationbeganinEuropein1987inNorwayandwasfollowedquicklyintheUnitedStatesbytheDallasNorthTurnpikein1989.Alsoduringthistime,thePortAuthorityofNewYorkandNewJerseybegancommercialoperationofRFIDforbusesgoingthroughtheLincolnTunnel.RFIDwasfindingahomewithelectronictollcollection,andnewplayerswerearrivingdaily.TagswerenowbeingbuiltusingcustomCMOSintegratedcircuitscombinedwithdiscretecomponentsform