Antenna-Based Passive UHF RFID Sensor Tags

102 Pages·2013·7.2 MB·English

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: [phone]
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
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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
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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
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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
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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