Antenna-Based Passive UHF RFID Sensor Tags PDF
Preview Antenna-Based Passive UHF RFID Sensor Tags
Thesis for the degree of Doctor of Technology Sundsvall 2013 Antenna-Based Passive UHF RFID Sensor Tags - Design and Application Jinlan Gao Supervisors: Professor Hans-Erik Nilsson Doctor Johan Side´n Department of Electronics Design Mid Sweden University, SE-851 70 Sundsvall, Sweden ISSN 1652-893X Mid Sweden University Doctoral Thesis 157 ISBN 978-91-87103-99-5 Akademiskavhandlingsommedtillsta˚ndavMittuniversitetetiSundsvall framla¨ggstilloffentliggranskningfo¨ravla¨ggandeavteknologiedoktorsexamen, tisdagenden18juni2013,klockan13:15isalO102,MittuniversitetetSundsvall. Seminarietkommerattha˚llaspa˚ engelska. Antenna-Based Passive UHF RFID Sensor Tags - Design and Application JinlanGao ⃝cJinlanGao,2013 DepartmentofElectronicsDesign MidSwedenUniversity,SE-85170Sundsvall, Sweden Telephone: +46(0)60148835 PrintedbyKopieringenMittuniversitetet,Sundsvall,Sweden,2013 Abstract RFID,asalowcosttechnologywithalonglifetime,providesgreatpotentialfor transmitting sensor data in combination with the ordinary ID number. The sensor can, for example, be integrated either in the chip or in the antenna of an RFID tag. Thisthesisfocusesonthedesignofantenna-basedUHFRFIDsensortagsaswireless sensors at the lowest possible cost level compatible with standard communication systemsinlogistics. Theapplicationsofthesensortags,inthiswork,mainlytarget remotehumiditysensing. Antenna-basedsensoryUHFRFIDtagsutilizetheinfluencethatthephysicalor chemicalparameterstobesensedhaveontheelectricalpropertiesofatagantenna. The variations of the electrical properties of the tag antenna can be measured in many ways. In the thesis, a description is provided as to how these variations are normallymeasuredbyanRFIDreaderwithoutanyotherassistantequipment. Threestructuresofantenna-basedRFIDsensortagsarepresentedwithdetailed characterizations.Thefirstoneutilizesthesensitivityoftheantennatothesurround- ing environment to construct RFID sensor tags, where a moisture absorbing layer providingwetness/humiditysensorfunctionalityisplacedontheRFIDtagantenna to increase the humidity concentration surrounding the tag antenna and the thesis describes how to overcome certain limitations due to disturbances associated with backgroundmaterials. Thesecondstructuredirectlyintegratesasmallresistivesen- sorelementintoanRFIDtagantennaandthesensorinformationcanthusmodulate theantennaperformancebymeansofgalvaniccontact. Thethirdstructureembeds a small resistive sensor element into a loop which is positioned on top of the tag antenna and the sensor information can thus modulate the performance of the tag antenna by means of electromagnetic coupling. Both theoretical analysis and full wave simulations are presented for the latter two sensor tag structures in order to characterizetheperformanceofthesensortags. An ultra-low cost printed humidity sensor with memory functionality is also designed and thoroughly characterized for integration into RFID tag antennas by means of galvanic contact or electromagnetic coupling. The sensor is a 1-bit write- once-read-many(WORM)memoryprintedusingconductiveink.TheWORMworks asapureresistivehumiditysensorandcanprovideinformationaboutanhistorical event. The WORM sensor is presented by introducing its geometry, characterizing its behavior in humidity and explaining the principle of the humidity effect. The WORM sensors are also integrated into the RFID tags by means of both galvanic contactandelectromagneticcouplinginordertoexperimentallyverifythetwocon- cepts. To lower the cost of the RFID tags, the antennas are normally printed, milled or etched on flexible substrates using low-cost high-speed manufacturing methods whichinsomecasescauseahighdegreeofedgeroughness.Theedgeroughnesswill affectthebehavioroftheantenna,however,thecharacteristicsofedgeroughnesson iii iv RFID antennas have previously not received any significant attention. Unforeseen antennabehaviorcanaffecttheantenna-basedsensortags,thustheinfluenceofedge roughnessisalsoinvestigatedinthethesis. Sammandrag RFID, som en la˚gkostnadsteknik med en la˚ng livsla¨ngd, tillhandaha˚ller en stor potentialfo¨ro¨verfo¨ringavsensordataikombinationmeddetordinarieID-numret. Sensorn kan till exempel integreras i RFID-chippet eller i en RFID-taggs antenn. Denna avhandling fokuserar pa˚ design av antenn-baserade sensortaggar fo¨r RFID pa˚ UHF-bandet som tra˚dlo¨sa sensorer till la¨gsta mo¨jliga kostnad, kompatibla med standard-kommunikationssysteminomlogistik. Applikationernafo¨rsensortaggar,i detha¨rarbetet,riktarsigfra¨mstmotfja¨rravla¨sningavfukt. Antennbaserade sensoriska UHF RFID-taggar utnyttjar den pa˚verkan som de fysikaliskaellerkemiskaparametrarsomskallavka¨nnasharpa˚ deelektriskaegen- skaperna hos en taggs antenn. Variationerna hos de elektriska egenskaperna hos taggens antenn kan ma¨tas pa˚ flera vis. I avhandlingen ges en beskrivning av hur dessavariationernormaltma¨tsmedenvanligRFID-la¨sareutanna˚gonannanassis- terandeutrustning. Tre stycken strukturer av antennbaserade RFID-sensortaggar presenteras med en detaljerad karakterisering. Den fo¨rsta utnyttjar antennens ka¨nslighet till den omgivande miljo¨n fo¨r att konstruera RFID-sensortaggar. I detta koncept tja¨nar ett fuktabsorberande material till att tillhandaha˚lla sensorfunktionalitet fo¨r va¨ta/fukt ochplaceraspa˚ RFID-antennenfo¨ratto¨kakoncentrationenavluftfuktighetenkring taggensantennochavhandlingenbeskriverhurmankano¨vervinnavissabegra¨ns- ningar pa˚ grund av osa¨kerheter i samband med bakgrundsmaterial. Den andra strukturen integrerar ett litet resistivt sensorelementet direkt i en RFID-taggs an- tenn och sensorinformationen kan da¨rmed modulera antennens prestanda genom galvanisk kontakt. Den tredje strukturen ba¨ddar in ett litet resistivt sensorelement ienloopstruktursoma¨rplaceradstraxovanfo¨rtaggensantennochsensorinforma- tionen kan da¨rmed modulera antennens prestanda genom elektromagnetisk kop- pling. Ba˚de teoretiska analyser och fullva˚gs-simuleringar presenteras fo¨r de tva˚ sistna¨mnda sensortagg-strukturerna i syfte att karakterisera sensortaggarnas pre- standa. Enfuktsensorsomkantryckastillva¨ldigtla˚gkostnadsamtharminnesfunktion- aliteta¨rocksa˚ designadochgrundligtkarakteriseradfo¨rintegreringiRFIDtaggars antennerviagalvaniskkontaktellerelektromagnetiskkoppling.Sensorna¨rett1-bits write-once-read-many (WORM) -minne tryckt med ledande bla¨ck baserat. WOR- Men fungerar som en rent resistiv fuktsensor och kan tillhandaha˚lla information om en historisk ha¨ndelse. WORM-sensorn presenteras genom att introducera dess geometri,karakteriseradessbeteendeifuktochfo¨rklaraprincipenavfukteffekten. WORM-sensorernaintegrerasocksa˚iRFID-taggarmedhja¨lpavba˚degalvaniskkon- taktochelektromagnetiskkopplingfo¨rattexperimentelltverifieradetva˚koncepten. Fo¨r att sa¨nka kostnaden fo¨r RFID-taggar a¨r antennerna normalt tryckta, fra¨sta elleretsadepa˚flexiblasubstratmedhja¨lpavbilligametoderfo¨rho¨ghastighetstillverk- ningsomivissafallkanorsakaenho¨ggradavkantoja¨mnhet.Kantoja¨mnhetpa˚verkar v vi en antenns egenskaper, men kantoja¨mnhet pa˚ RFID-antenner har tidigare inte fa˚tt na˚gonsto¨rreuppma¨rksamhet.Ofo¨rutsettantennbeteendekanpa˚verkaantennbaser- adesensortaggarvarfo¨rkantoja¨mnhetunderso¨ksocksa˚ idennaavhandling. Acknowledgements First I would like to thank my supervisors Dr. Johan Side´n and Prof. Hans- Erik Nilsson for giving me the opportunity and employing me as a Ph.D. student. Thanks to Johan for all the guidance, suggestions and ideas on my research work during these years, and for always believing me and supporting me. Without his patienceandencouragement,thisthesiswouldnothavebeenpossible. Alsothanks toHans-Erikforthesupervisionandconsistentsupportonmyresearchwork. Thanks to Henrik Andersson and Anatoliy Manuilskiy for all their help in my researchwork. Thanks to Prof. Youzhi Xu for introducing me to this opportunity to start my Ph.D.studyatMidSwedenUniversity. I would also like to thank all my colleagues at the Electronics Design Division, MidSwedenUniversityforyourkindnessandfriendliness. AlsomanythanksshallbegiventoallmyChinesefriendswhomImetinSundsvall forbringinghappinesstomylife. FinancialsupportfromMidSwedenUniversity,theSwedishKKFoundation,the Research Council Formas and the EU FP7 Project PriMeBits is also gratefully ac- knowledged. Lastbutnotleast,thankstomyfamiliesfortheirendlessloveandsupport. Spe- cialthankstomydearhusbandforstandingbehindmeinallthatIdo. Sundsvall,May2013 JinlanGao vii viii Table of Contents Abstract iii Sammandrag v Acknowledgements vii TableofContents ix ListofPapers xiii ListofFigures xv Terminology xvii 1 Introduction 1 1.1 Maincontributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 AcquisitionoftheSensorInformationforanAntenna-BasedSensorTag 7 2.1 Measurableoutputvariables. . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 Measurementsetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3 UHFRFIDSensorTagsWithCoveringofSensingMaterial 13 3.1 Experimentalresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1.1 Power-updifferencesduetowaterdrops . . . . . . . . . . . . . 15 3.1.2 Power-updifferencesduetohumidity . . . . . . . . . . . . . . . 15 3.2 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4 PrintedSensor(WORM) 19 4.1 DesignofPrintedSensor . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.2 TemperatureSintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.3 HumiditySintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.4 CombinationEffectofTemperatureandHumidity . . . . . . . . . . . . 23 4.5 Solventeffectontheresistanceofprintedpatterns . . . . . . . . . . . . 24 4.6 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5 UHFRFIDTagswithPassiveSensorsDirectlyIntegratedintotheAntennas 31 5.1 AnalysisModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 5.2 AntennaDesigns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 5.3 ExperimentalResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 5.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 ix x TABLEOFCONTENTS 6 UHF RFID Tags with Passive Sensors Electromagnetically Coupled to the Antennas 45 6.1 Analysismodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 6.1.1 ForShunt/SeriesInductorsMatchedAntenna . . . . . . . . . . 46 6.1.2 ForInductivelyCoupledAntenna . . . . . . . . . . . . . . . . . 52 6.2 DesignConsiderations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 6.2.1 DifferentTypesofAntennas . . . . . . . . . . . . . . . . . . . . . 56 6.2.2 DifferentTypesofChips . . . . . . . . . . . . . . . . . . . . . . . 57 6.2.3 VariousDistancebetweencouplingloopandtagantenna. . . . 57 6.2.4 Assistanceoftheadditionalembeddedcomponent . . . . . . . 59 6.3 Experimentalvalidation . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 6.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 7 Investigationontheeffectoftheedgeroughnessontheantenna 65 7.1 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 7.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 7.2.1 Inputreturnloss . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 7.2.2 Bandwidth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 7.2.3 Ohmiclosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 7.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8 Summaryofpublications 71 8.1 PaperI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.2 PaperII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.3 PaperIII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 8.4 PaperIV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.5 PaperV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.6 PaperVI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 8.7 PaperVII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8.8 PaperVIII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8.9 PaperIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 8.10 PaperX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 8.11 Author’scontributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 9 ThesisSummary 77 References 79 PAPERI 85 PAPERII 91 PAPERIII 97 PAPERIV 111 PAPERV 117
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