RadioFrequencyIdentification(RFID)systemsuse
radiofrequencytoidentify,locateandtrackpeople,
assets,andanimals.PassiveRFIDsystemsare
composedofthreecomponents–aninterrogator
(reader),apassivetag,andahostcomputer.Thetag
iscomposedofanantennacoilandasiliconchipthat
includesbasicmodulationcircuitryandnon-volatile
memory.Thetagisenergizedbyatime-varying
electromagneticradiofrequency(RF)wavethatis
transmittedbythereader.ThisRFsignaliscalleda
carriersignal.WhentheRFfieldpassesthroughan
antennacoil,thereisanACvoltagegeneratedacross
thecoil.Thisvoltageisrectifiedtosupplypowertothe
tag.Theinformationstoredinthetagistransmitted
backtothereader.Thisisoftencalledbackscattering.
Bydetectingthebackscatteringsignal,theinformation
storedinthetagcanbefullyidentified.AN680PassiveRFIDBasicsAuthor:PeteSorrellsModulationMicrochipTechnologyInc.Periodicfluctuationsintheamplitudeofthecarrierusedtotransmitdatabackfromthetagtothereader.SystemsincorporatingpassiveRFIDtagsoperateinINTRODUCTIONwaysthatmayseemunusualtoanyonewhoalreadyRadioFrequencyIdentification(RFID)systemsuseunderstandsRFormicrowavesy
暂无评论