2023学年完整公开课版RFIDAntennaClassification（2022新）

Presenter:MiZhiqiangHunanModernLogisticsCollegeRFIDAntennaClassificationContents1PrincipleofRFIDTechnology2RFIDantennatype3RFIDantennadesignUsually,theapplicationsystemofRFIDismainlycomposedofreaderandRFIDcard,asshowninFigure1.Thereaderisgenerallyusedasacomputerterminaltoread,writeandstorethedataoftheRFIDcard.Itconsistsofcontrolunit,highfrequencycommunicationmoduleandantenna.TheRFIDcardisapassivetransponder,mainlycomposedofanintegratedcircuit(IC)chipanditsexternalantennagroup.Amongthem,RFIDchipsareusuallyintegratedwithRFfront-end,logiccontrol,memoryandothercircuits,andsomeevenintegrateantennasonthesamechip.ReaderMemoryRFfront-endLogiccontrolTransponderComputer01PrincipleofRFIDTechnologyAntennaplaysakeyroleindatacommunicationbetweenRFIDcardandreader.Ontheonehand,thepassiveRFIDcardchipneedsenoughenergytostartthecircuitthroughtheantennaintheelectromagneticfieldgeneratedbythereaderantenna;ontheotherhand,theantennadeterminesthecommunicationchannelandmodebetweentheRFIDcardandthereader.Atpresent,RFIDhasbeenwidelyused,andthereareseveralinternationalstandards:ISO10536,ISO14443,ISO15693,ISO18000andsoon.Thesestandardsnotonlyspecifythecommunicationdataframeprotocol,butalsospecifythetechnicalspecificationsrelatedtoantennaphysicalcharacteristics,suchasworkingdistance,frequencyandcouplingmode.ThestandardsettingofRFIDapplicationsystemdeterminesthechoiceofRFIDantenna.ThefollowingwillintroducevarioustypesofRFIDantennawhichhavebeenwidelyusedandtheirperformances.01PrincipleofRFIDTechnologyTherearemanykindsofRFIDantennasfordifferentfrequencies,differentuses,differentoccasions,differentrequirementsandotherdifferentsituations.Formanykindsofantennas,itisnecessarytoclassifythemproperly.ClassificationbyworkingfrequencybandShortwaveantennaUltrashortWaveAntennaMicrowaveantennaOmnidirectionalantennadirectionalantennaPlanarantennaLinearantennaCoiltypeMicrostrippatchDipoletypeClassifiedbydirectionClassifiedbyshapeClassifiedbyantennadesignprocess02RFIDantennatype(1)CoilAntennaTheinteractionbetweentheRFIDantennaandthereaderantennaissimilartothatofatransformerwhentheRFIDcoilantennaentersthealternatingmagneticfieldgeneratedbythereader.Thecoilsofthetwoantennasareequivalenttotheprimarycoilandthesecondarycoilofthetransformer.02RFIDantennatype(2)DipoleAntennaDipoleantenna(alsoknownassymmetricaldipoleantenna)isthemostcommonlyusedinlong-distancecoupledRFIDapplications.Thedipoleantennaiscomposedoftwostraightwiresofthesamethicknessandlength,andthesignalisfedfromthetwoendsinthemiddle.02RFIDantennatypeThedipoleantennaanditsevolutionformareshowninFig.2-8.Thedipoleantennaconsistsoftwostraightwiresofthesamethicknessandlength,andthesignalisfedfromthetwoendsinthemiddle,whichwillproduceacertaincurrentdistributiononthetwoarmsofthedipole.Theelectromagneticfieldisexcitedinthespacearoundtheantenna,andtheradiationfieldequationcanbeobtainedbyMaxwell'sequation.Intheformula,Izisthecurrentdistributedalongtheoscillatorarm,αisthephaseconstant,risthedistancefromthecenteroftheoscillatortotheobservationpoint,θistheanglebetweentheaxisoftheoscillatorandr,listhelengthofasingleoscillatorarm.Similarly,theinputimpedance,inputecholossS11,impedancebandwidthandgainoftheantennacanalsobeobtained.(2)DipoleAntenna02RFIDantennatypeWhenlengthofasingleoscillatorarml=λ/4(half-waveoscillator),thereactancecomponentofinputimpedanceiszero.Theinputimpedanceoftheantennacanberegardedasapureresistance.Ignoringthetransverseinfluenceofantennathickness,simpledipoleantennadesigncantakethelengthofoscillatorlasintegertimesofλ/4.Forexample,ahalf-wavedipoleantennawithaworkingfrequencyof2.45GHz,whoselengthisabout6cm,canbeoperatedwithafoldedoscillatorwhentheinputimpedanceofthedipoleantennaisrequiredtobelarge.(a)Dipoleantenna;(b)Foldeddipoleantenna;(c)Deformeddipoleantenna(2)DipoleAntenna02RFIDantennatypeDipoleAntenna(3)MicrostripPatchAntenna1)DefinitionandStructureofMicrostripAntennaMicrostripantennaisanantennaformedbyplacingathinconductorsheetonadielectricsubstratewithaconductorgroundingplate.Itusesmicrostriporcoaxiallinefeederstoexcitetheradiofrequencyelectromagneticfieldbetweentheconductorpatchandthegroundingplate,andradiatesoutwardthroughthegapbetweenthepatchandthegroundingplate.Therefore,microstripantennacanalsobeseenasaslotantenna.Generally,thethicknessofdielectricsubstrateisverysmallcomparedwiththewavelength,soitrealizesone-dimensionalminiaturizationandbelongstothecategoryofsmallelectricantenna.Microstripantennaform02RFIDantennatypeGroundplateConductorsheetMicrostripfeederDielectricsubstrate2)Advantages,DisadvantagesandApplicationsofMicrostripAntennasComparedwithconventionalmicrowaveantennas,microstripantennashavethefollowingadvantages:Thinsection,smallvolumeandlightweight;Ithasplanarstructureandcanbemadeintoconformalstructurewithmissiles,satellitesandothercarriers.Feednetworkcanbemadewithantennastructure,andcanbemassproducedbyprintedcircuittechnology.Itcanbeintegratedwithactivedevicesandcircuitsasasinglemodule.Itiseasytoachievecircularpolarizationanddual-band,dual-polarizationandothermulti-functionalwork.Themaindrawbacksofmicrostripantennasare:Thebandisnarrow.Thereareconductoranddielectriclosses,andsurfacewaveswillbestimulated,resultinginreducedradiationefficiency.Powercapacityissmall,generallyusedinmediumandsmallpoweroccasions;performanceisgreatlyaffectedbysubstratematerials.However,manytechnologieshavebeendevelopedtoovercomeorreducetheseshortcomings.(3)MicrostripPatchAntenna02RFIDantennatypeRectangularmicrostripantennaanditsmainsurfacepattern3)MicrostripAntennaWorkingPrincipleThemicrostrippatchantennaiscomposedofaradiationpatchconductorattachedtoadielectricsubstratewithametalfloor.Asshowninthefigure,thepatchconductorcanbedesignedinvariousshapesaccordingtotheradiationcharacteristicsoftheantenna.Thedistancebetweentheradiatingconductorofthepatchantennaandthemetalfloorisafewtenthsofawavelength.Assumingthattheradiatedelectricfielddoesnotchangealongthelateralandlongitudinaldirectionsoftheconductor,andonlyvariesalongthelengthoftheconductorofabouthalfwavelength(λg/2),Theradiationofthemicrostrippatchantennaisbasicallycausedbythefringefieldoftheopenedgeofthepatchconductor,andtheradiationdirectionisbasicallydetermined.(3)MicrostripPatchAntenna02RFIDantennatypeEx

distributionCalculatedvalueTestvalueH-planeE-planeCalculatedvalueTestvalueMicrostripantennaGenerally,itissuitableforRFIDwithlittlechangeincommunicationdirection.Intheapplicationsystem,inordertoimprovetheperformanceoftheantennaandconsiderthecommunicationdirectivityproblem,variousmicrostripslotantennashavebeenproposed,andakindofworkingat2.4GHzisdesigned.Asingleslotantennaanda5.9GHzdualslotantennahaveradiatedwavesaslinearlypolarizedwaves;acircularlypolarizedslot-coupledpatchantennahasbeendevelopedwhichcanuseleft-handcircularpolarizationandright-handcircularpolarizationtobinary'1'and'0'inthedataareencoded.(3)MicrostripPatchAntennaDielectricsubstrateDielectricsubstrateMetalflooringPatchMetalflooringRadiationpatch02RFIDantennatype4)CircularlyPolarizedMicrostripAntennaAnantennathatradiatesorreceivesacircularlypolarizedwaveiscalledacircularlypolarizedantenna.Ithasthefollowingimportantproperties.Acircularlypolarizedwaveisanequalamplitudeinstantaneousrotatingfield.Thatis,alongthedirectionofitspropagation,theendpointtrajectoryoftheinstantaneouselectricfieldvectorofthewaveisacircle.Acircularlypolarizedwavecanbedecomposedintotwoequal-widthpolarizedwavesthatarebothspatiallyandtemporallyorthogonal.Anypolarizedwavecanbedecomposedintotwocircularlypolarizedwaveswithoppositedirectionsofrotation.Iftheantennaradiatesaleft-handedcircularlypolarizedwave,itonlyreceivestheleft-handedcircularlypolarizedwaveanddoesnotreceivetheright-handedcircularlypolarizedwave;conversely,iftheantennaradiatesaright-handedcircularly-polarizedwave,onlytheright-handedcircularlypolarizedwaveisreceived.Thisiscalledtherotationalorthogonalityofacircularlypolarizedantenna.Whenacircularlypolarizedwaveisincidentonasymmetricaltarget(suchasaplane,asphericalsurface,etc.),thereflectedwavebecomesreverse-rotating,thatis,theleft-handedwavebecomesright-handed,andtheright-handedwavebecomesleft-handed.(3)MicrostripPatchAntenna02RFIDantennatype5)BroadbandMicrostripAntennaWiththeincreasinguseofmicrostripantennas,therearemanyeffectivemethodsforhowtowidenthebandwidthofmicrostripantennas.Fromthecurrentsituation,therearemainlythefollowingmethods(l)reducetheequivalentcircuitQvalue:increasethesubstratethicknessh,reducetherelativedielectricconstantandincreasea,b(rectanglepatchcase),etc.;(2)usingamulti-layerstructure;(3)anadditionalimpedancematchingnetwork;(4)microstripantennapatchgrooving;(5)Usingslotcouplingpowerfeedingandthelike.(3)MicrostripPatchAntenna02RFIDantennatype6)Capacitor-CoupledFedMicrostripAntennaDiagramofcapacitor-coupledelectricallymicrostripantenna(3)MicrostripPatchAntennaGroundingplate02RFIDantennatype7)Basestationantenna,repeaterantennaandindoorantennacommonlyusedinmobilecommunicationBasicKnowledgeofPlateAntennaWhetheritisGSMorCDMA,slabantennaisoneofthemostcommonandimportantbasestationantennas.Theadvantagesofthisantennaare:highgain,goodsectorpattern,smallbacklobe,convenientcontrolofverticalplanepattern,reliablesealingperformanceandlongservicelife.Plateantennaisoftenusedasuserantennaofrepeaterstation.Accordingtotherangeofsector,theantennatypeshouldbeselected.Intheformationofhighgainplateantenna,multiplehalf-waveoscillatorsarearrangedinaverticallineararray.(3)MicrostripPatchAntenna02RFIDantennatypeVerticalplanepatternofsinglehalf-waveoscillatorGainG=2.15dB(3)MicrostripPatchAntenna02RFIDantennatypeAddareflectingplatetothesideofthelineararray(taketheverticalarrayoftwo-halfwaveoscillatorswithreflectingplateasanexample)(3)MicrostripPatchAntenna02RFIDantennatypeFourHalf-WaveOscillatorsVerticalplanepatternofsinglehalf-waveoscillatorGainG=2.15dBA:Lineararraywithmultiplehalf-waveoscillatorsarrangedverticallyVerticalplanepatternoftwohalf-waveoscillatorsGainG=5.15dBVerticalplanepatternoffourhalf-waveoscillatorsGainG=8.15dBTwoHalf-WaveOscillatorsSinglehalf-waveoscillatorC.Inordertoimprovethegainofplateantenna,eighthalf-waveoscillatorarrayscanbefurtherused.(3)MicrostripPatchAntennaB:Addareflectortothesideofthelineararray(taketheverticalarrayoftwohalf-waveoscillatorswithareflectorasanexample)VerticalPlanePatternsofTwoHalf-WaveOscillators(withReflectors)Horizontalpatternoftwohalf-waveoscillators(withreflectors)GainG=11-14dBTheConfigurationofTwoHalf-WaveOscillators(withReflector)ontheVerticalPlaneConfigurationofTwoHalf-WaveOscillators(withReflector)ontheHorizontalLevelThelengthofthereflectorisLThewidthofthereflectorisWTwoHalf-WaveOscillatorsTwoHalf-WaveOscillators02RFIDantennatype2)HighGainGridParabolicAntennaStartingfromtheperformance-priceratio,peopleoftenchoosethegridparabolicantennaasthedonorantennaofrepeater.Becauseofthegoodfocusingeffectoftheparabolicmask,theparabolicantennahasastrongabilitytocollectradiation.Thegratingparabolicantennawithadiameterof1.5mhasagainofG=20dBin900MHzband.Itisespeciallysuitableforpoint-to-pointcommunication,forexample,itisoftenselectedasadonorantennaforrepeaters.Theparaboloidusesagridstructure,oneistoreducetheweightoftheantenna,theotheristoreducethewindresistance.Parabolicantennacangenerallygiveafront-to-backratioofnolessthan30dB,whichisthetechnicalindexthatrepeatersystemmustmeetforreceivingantennatopreventself-excitation.(3)MicrostripPatchAntenna02RFIDantennatype3)YagiDirectionalAntennaTheYagidirectionalantennahastheadvantagesofhighgain,lightweightstructure,convenienterectionandlowcost.Therefore,itisespeciallysuitableforpoint-to-pointcommunication,forexample,itisthepreferredtypeofantennaforoutdoorreceivingantennaofindoordistributionsystem.ThemorethenumberofelementsofYagidirectionalantenna,thehigheritsgain.Usually,Yagidirectionalantennawith6-12elementsisused,anditsgaincanreach10-15dB.(3)MicrostripPatchAntenna02RFIDantennatyp