无源RFID的基础知识

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