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Research ArticlePower Transmission of UHF Passive Embedded RFID in Tires
Shengbo Hu12 Bing Si3 Heng Shu12 and Jinrong Mo12
1 Institute of Intelligent Information Guizhou Normal University Guiyang 550001 China2Department of Guizhou Education Center for RFID and WSN Engineering Guiyang 550001 China3 Institute of New Technology Guizhou Academy of Sciences Guiyang 550001 China
Correspondence should be addressed to Shengbo Hu hsbnsscaccn
Received 5 August 2013 Revised 28 December 2013 Accepted 30 December 2013 Published 17 February 2014
Academic Editor Yuan Yao
Copyright copy 2014 Shengbo Hu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
UHF passive RFID tags embedded in tires have a deep impact on tire life cycle management and tire monitoring In this workwe present the power transmission of UHF passive embedded RFID in tires In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes through air and tires The total path loss contains reflection loss at tire-airboundaries and attenuation loss in the tires The power transmission is based on the permittivity of tires and tire-air boundaryconditions We give an OCP method for measuring the permittivity of tires By analyzing the radio link for UHF passive RFID weestablish a model of wave propagation of UHF embedded RFID in tires and make numerical analyses Numerical analyses showthat the error of the OCP methods for measuring the permittivity of tires is small the parallel polarization and normal incidenceof wave are chosen for improving the performance of the UHF embedded RFID in tires and distance is chosen to keep powertransmission function from locating valley
1 Introduction
Acting as sensors passive RFID tags can avoid sensor nodesbulky and battery powered For that reason UHF passive tagsembedded in tires have been used widely for tire life cyclemanagement in the USA and the European Union [1 2] Tomeet the Automotive Industry Action Grouprsquos B-11 standardfor North AmericanMichelin began offering automakers theoption of purchasing tires with embedded tags [3] Besidesthe combinations of UHF passive tags embedded in tire andtire pressure monitoring are paid attention highly to improvethe reliability of tire and tire control systems [4]
However range has been one of the hardest challengesin UHF passive RFID embedded in tires because the rubbermakes it harder to read the tag When Michelin took off-the-shelf UHF passive tags and embedded them in tires theread distance dropped to less than three inches [3] The maindifference between the common RFID and RFID embeddedin tires is communication medium which attenuates RFpower from the reader in RFID embedded in tires Toimprove the range and reliability of RFID embedded intires it is of great concern to study power transmission of
wave propagation for UHF passive embedded RFID in tiresbecause the tags do not contain any battery and rely on theelectromagnetic field for both power and communicationIn this paper we present the power transmission of wavepropagation for UHF passive embedded RFID in tires andlay out the foundations for reliable communication in thisenvironment
InUHFpassive RFID systems a bidirectional radio link isestablished between reader and tags which can be classifieda forward link from the reader to tags and a backward linkfrom the tags to reader [5] Depending on the characteristicsof reader and tags the propagation channel properties likepath loss and fading the power transmission coefficient andthe channel transmissions are investigated in [5ndash7] In UHFpassive embedded RFID systems in tires the bidirectionalradio link between reader and tags goes through air and tiresThe total path loss contains several factors reflection lossdue to reflected power at tire-air boundaries attenuation lossin the tires and spreading loss which is simply due to theradiation properties of antenna Each of these factors can beanalyzed using the permittivity of tires and tire-air boundaryconditions
Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2014 Article ID 897041 8 pageshttpdxdoiorg1011552014897041
2 International Journal of Antennas and Propagation
FlangeOuter conductor
Dielectric
Coaxial probe
120576lowast
Test materialInner conductor
(a) Measuring system
z
Flange 120588
2a
2b Coa
xial
prob
e
(b) Geometrymodel
Figure 1 Measuring reflection coefficients with open ended coaxialprobe
So this paper focuses on wave propagation for UHFpassive embedded RFID in tires based on the permittivityof tires and tire-air boundary conditions Hence Section 2presents how to measure the permittivity of tires Section 3describes the radio link for UHF RFID systems Section 4gives a propagation model of UHF passive embedded RFIDsystems in car tires Section 5 describes numerical calculationand discussion Section 6 concludes this paper
2 Measuring the Permittivity of Tires
21 Measuring the Permittivity Several techniques have beendeveloped for measuring the permittivity [8ndash10] Howeversome such as resonant cavity or wave-guide transmissionline cells require test hardware machining and destructiveprocessing And open ended coaxial probe (OCP) techniqueis currently one of themost popular techniques formeasuringthe permittivity OCP technique can performnondestructivebroadband (RF andmicrowave bands) and high temperaturemeasurement Its well-developed theory makes it possible toobtain sufficiently accurate results
A schematic for a coaxial open ended probe is shown inFigure 1 To reduce significantlymeasuring error thematerialbeing tested is placed in close contact with the probersquosflat end The reflection coefficient measured with a vectornetwork analyzer (VNA) is used as inverse calculation of thepermittivity of the material
An equivalent circuit of admittance model for a coaxialopen ended probe is shown in Figure 2 In Figure 2 119884
119888is
the probe characteristic admittance and 119884(120596 120576lowast
) is the loadadmittance including the inner admittance 119884
119894(120596) = 119895120596119862
119894
of the capacitance 119862119894between outer conductor and inner
conductor and the outer admittance 119884119900(120596 120576lowast
) obtained bysolving the following equation [11]
119884119900
(120596 120576lowast
) = 11989521205961205760120576lowast
[ln(119887119886)]2∬
119887
119886
int
120587
0
cos120593119890minus119895119896119903
1199031198891205931198891205881015840
119889120588 (1)
where 119896 = 120596radic1205831205761015840 120583 is the permeability 120596 is the oper-ating frequency (120588 120588
1015840
120593) are cylindrical coordinates 119903 =
[1205882
+ 12058810158402
minus 21205881205881015840 cos120593]
12 and 119886 and 119887 are respectively the
YcProbe
Ci 120576lowastC0 1205962(120576lowast)2C2
1205962(120576lowast)15C1
Figure 2 The equivalent circuit of admittance model for a coaxialopen ended probe
interior and the external radius of the probe And (1) can bethe series expansion form of (2)
119884119900
(120596 120576lowast
) =
infin
sum
119899=0
(minus1) (minus119895120596)119899+1
119862119899120576lowast(119899+2)2
(2)
where
119862119899
=2(12058301205760)(119899+2)2
1198991205830[ln(119887119886)]
2∬
119887
119886
int
120587
0
119903119899minus1 cos120593119889120593119889120588
1015840
119889120588 (3)
Equation (3) shows that 119862119899is constant For convenience (2)
can be truncated to 3 terms with the 1198620 1198621 and 119862
2 So
119884(120596 120576lowast
) can be given as below
119884 (120596 120576lowast
) = 119895120596119862119894+ 119895120596120576
lowast
1198620
+ 1205962
(120576lowast
)15
1198621
+ 1198951205963
(120576lowast
)2
1198622
(4)
where 120576lowast
1198620
is the fringing capacitance of the probe1205962
(120576lowast
)2
1198622is the fringing capacitance generated from a
test material and 1205962
(120576lowast
)15
1198621is the equivalent conductance
radiated from the probeThe load admittance 119884(120596 120576
lowast
) can be obtained from theEM wave reflection coefficient Γ(120596 120576
lowast
) using the followingrelation
119884 (120596 120576lowast
) = 119884119888
1 minus Γ (120596 120576lowast
)
1 + Γ (120596 120576lowast) (5)
Hence measuring the permittivity can be performedusing the following steps
Step 1 Using VNA we measure the four different reflectioncoefficients Γ
1 Γ2 Γ3 and Γ
4associated with the four different
frequencies using a standard material with the known per-mittivity Using (4) and (5) the four unknown parameters119862
119894
1198620 1198621 and 119862
2can be solved
Step 2 Using VNA we measure the reflection coefficientsΓ associated with some frequencies using the test materialUsing (4) and (5) the permittivity of the test material can becalculated by a suitable iterative method
22 Measurement Setup for Tires The tire sidewall and theposition of the RFID tag embedded in tire are displayed inFigure 3The tag is embedded parallel to the outer steel mesh
International Journal of Antennas and Propagation 3
Steel
Inner diameterRFID tag
Tire sidewall rubber
Figure 3 The RFID tag embedded in tires
Coaxial cableProbe
Tire specimen
ManipulatorTemperature sensor
VNAAV 3629A
ScrewThermometer
Figure 4 The OCP measurement system
at a distance that depends on the tire size and ranges from 4to 8 cm above the inner steel mesh [1]
To reduce significantly measuring error using OCP tech-nique the tire sidewall specimen has to meet the followingconditions
(i) The surface of the tire sidewall specimen has to be flatA piece of the tire sidewall is cut out and the crosssection is polished to obtain a flat surface
(ii) The specimen has to have semi-infinite thickness sothat the penetration of the fieldmust bemuch smallerthan the specimenrsquos thickness
(iii) There must not be air gaps between probe and the tiresidewall specimen
Figure 4 illustrates an OCP measurement system Thesystem consists of a VNA a thermometer a coaxial probeand a manipulator with screw for fixing the tire sidewallspecimen Tightening the screw the probe is pressed againstthe specimen until no more variation of the measurementresults is observed
23 Simulation Verifying Using HFSS Simulation verifyingusing HFSS to verify the measurement accuracy using OCPtechnique an OCP model using HFSS (high frequency
x
y
z
Air boxPort
Open ended coaxial probe
Tire sidewall material
Figure 5 OCP model based on HFSS
structure simulator) is set up to compare Given themeasuredpermittivity of tire specimen using the measuring methodspresented in Section 21 the reflection coefficient is solvedusing the OCPmodel And the simulation and measurementreflection coefficients are compared
The OCP model based on HFSS is shown in Figure 5In Figure 5 the inner and outer conductors of the probe aremade of gilded brass and the space between the inner andouter conductor is filled in Teflon dielectric material Thetire specimen is modeled as a cylinder To avoid perfectlyconducting boundaries around the tire sidewall material anair box is implemented that surrounds the whole simulationsetup
3 Radio Link for UHF Passive RFID
In passive UHF RFID systems a bidirectional radio link isestablished between reader and tags including a forward linkfrom the reader to tags and a backward link from the tagsto reader What radio link for UHF passive RFID differsfrom conventional radio is that the backward link resemblesradar link Besides the RFID tagrsquos antenna absorbs waves asa function of its load match and reemits waves as a functionof its load mismatch
31 Power Absorbing Coefficient RFID tag consists of anantenna and chip The impedance matching of tag antennaand chip strongly influences the RF power transmissionand the communication performance between reader andtags Because of IC technological limit the impedance of achip cannot be chosen arbitrarily [12] So the chiprsquos inputimpedance is designed to switch between two values betweenthe conjugate impedance called as absorbing impedance119885chip1 and other impedance called as reflecting impedance119885chip2 The quality of the impedance match can be definedby the power absorbing coefficient 120591 which is the poweraccepted by the chip and the available power 119875tag at theantenna port [5 12]
120591 =
4Re [119885ant]Re [119885chip1]
Re [119885ant + 119885chip1]2
+ Im [119885ant + 119885chip1]2 (6)
4 International Journal of Antennas and Propagation
where 119885ant is the tag antennarsquos input impedance and 0 le 120591 le
1 When 120591 = 1 all available power is absorbed by the chipAnd when 120591 = 0 no available power is absorbed by the chipSo the range of frequency that 120591 reaches a demand value isdefined as the bandwidth of the tag antenna This shows thata best designed tag antenna is very important to improve theperformance of UHF passive RFID
32 Power Transmission Coefficient In a passive RFID thepower absorbed by the chip in forward link can be expressedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (7)
where119875TXreader is the transmitted power from reader and119875chipmust be higher than the tagrsquos sensitivity for the tagrsquos normalwork And |119878
21|2 is the power transmitted coefficient in the
forward link depending on the antenna power transmissionof reader and tag (eg antenna gain) and the propagationchannel properties like path loss and fading [5]
The power received by the reader from the tag can beexpressed as in the backward link
119875RXreader =100381610038161003816100381611987812
1003816100381610038161003816
2
120578119875tag =100381610038161003816100381611987812
1003816100381610038161003816
2
120578100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (8)
where 120578 is the modulation efficiency which is defined as theratio of the power scattered by the tag and the power availableat the tag antenna output |119878
12|2 is the power transmitted coef-
ficient in the backward link As real propagation environmentis symmetrical |119878
12|2
= |11987821
|2
4 Model of Power Transmission ofUHF Passive RFID Embedded in Tires
41 Harmonic Waves For time-harmonic fields when themedium presents a conductivity 120590 and permeability 120583 at theoperating frequency 120596 a permittivity 120576
lowast the wave equationcan be written as a time-independent wave equation towards+119911 direction
nabla2
119864 minus 1205742
119864 = 0 (9)
nabla2
119867 minus 1205742
119867 = 0 (10)
minus1205742
= 1198962
(1 minus 119895 tan 120575) = 1205962
120583120576lowast
(11)
where 120576lowast
= 1205761015840
(1 minus 119895 tan 120575) and 119896 = 120596radic1205831205761015840 is the wave numbercorresponding to an unbounded lossless medium with a realdielectric constant 120576
1015840For uniform plane waves nabla
2
= 1205972
1205972
119911 so (9) and(10) have solutions of the form 119864119890
120574119911 and 119867119890120574119911 and the
instantaneous values for the fields are given as follows
= Re 119864119890minus120572119911
119890119895(120596119905minus120573119911)
= Re 119867119890minus120572119911
119890119895(120596119905minus120573119911)
(12)
Free space
R120579i
RFID reader
RFID tag
(a) RFID scenarios in free space
Free space
R120579i
RFID reader RFID tag
Tire
(b) RFID scenarios embedded in tire
Figure 6 RFID scenarios
where the attenuation constant 120572 and the phase constant 120573
can be expressed respectively as follows [13]
120572 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
minus 1]
12
120573 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
+ 1]
12
(13)
So the electric strength decreases with distance 119911 aregiven as
119864 = 1198640119890minus120572119911 cos120573119911 (14)
Substituting (14) into power equation we have
119875 = 1198750
1003816100381610038161003816cos 21205731199111003816100381610038161003816 119890minus2120572119911
(15)
42 Power Transmission for RFID Embedded in Tires TheRFID scenarios in space and embedded in tires are shown inFigure 6 In Figure 6 the incident angle of waves is 120579
119894
In the free space the absorbing power by the RFID tag isgiven as
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
4120587119877)
2
119866119879119875TXreader
(16)
where 120582 is the free space wavelength 119877 is the distance fromRFID reader and 119866
119879is the gain of the tagrsquos antenna
International Journal of Antennas and Propagation 5
In the scenarios embedded in tires (16) can be modifiedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
41205871198771
)
2
10038161003816100381610038161198791198881003816100381610038161003816
2
119866119879
1003816100381610038161003816cos 21205731198971003816100381610038161003816 119890minus2120572119897
119875TXreader
= 120591(120582
41205871198771
)
2
119866119905119879 (119891 120579
119894 119897) 119875TXreader
(17)
where 1198771is the distance between tires and the reader 119879
119888
is electric field transmission coefficient at boundary of tiresand free space and 119879(119891 120579
119894 119897) = |119879
119888|2
| cos 2120573119897|119890minus2120572119897 is power
transmission function depending on 120579119894and the distance 119897 in
tiresWhen a plane EM wave incident at an oblique angle
on tires interface there are two cases to be consideredincident electric field has polarization parallel to the planeof incidence and incident electric field has polarization thatis perpendicular to the plane of incidence So from theboundary conditions that is continuity of tangential electricand magnetic fields at the car tire interface and using theSnellrsquos laws of reflection and refraction the 119879
119888can be derived
as follows
Case 1 Parallel polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119905+ 1205780cos 120579119894
(18)
Case 2 Perpendicular polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119894+ 1205780cos 120579119905
(19)
5 Numerical Analyses
51 Measuring the Permittivity of Tires A standard tire(CPC220555 R16 91V) with the known permittivity (thepermittivity is 120576
1015840
= 35 and tan 120575 = 003 at frequency866MHz) is used to determine the parameters119862
11989411986201198621 and
1198622 Using the measuring methods presented in Section 21
119862119894 1198620 1198621 and 119862
2are 000113 pF 2324 times 10ndash14 pF 1518 times 10ndash
42 pF and 16345 times 10ndash50 pF respectivelyThe measuring results for reflection coefficients in a
Smith chart are shown in Figure 7 using a test car tire (GL274A made in Guizhou Tire Co LTD China) with a vectornetwork analyzer (AV 3629A) between 100MHz and 5GHzat room temperature Using (4) and (5) the permittivity ofthe test car tire can be determined to be 120576
1015840
= 378 andtan 120575 = 0038
Measuring and simulation results can be compared usingthe methods presented in Section 23 In the OCP modelthe inner and outer radiuses of the probe are 065mmand 235mm respectively The thickness of Teflon with arelative permittivity of 120576
1015840 and tan 120575 = 0001 is 135mm Thetest tire is modeled as a cylinder with a radius of 10mmand a height of 10mm The absolute error of the real partof simulation and measuring coefficients and the absolute
90100110120
130
140
150
160
170
180
minus170
minus160
minus150
minus140minus130
minus120
80 7060
50
40
30
20
10
0
minus10
minus20
minus30
minus40
minus50minus60
minus70minus80minus90minus100minus110
000000
020
020
050
050
100
100
200
200
500
500
minus500
minus200
minus020
minus050
minus100
Figure 7 Measured reflection coefficients of a test car tire
00 1 2 3 4 5
001
002
003
004
Absolute error of real partAbsolute error of imaginary part
Frequency (GHz)
Abso
lute
erro
r
Figure 8 Absolute error values of real part and imaginary part
error of the imaginary part of these versus frequency areshown in Figure 8 And the absolute error of the simulationand measuring coefficients is shown in Figure 9 Figures 8and 9 show that there is small deviation (lt0004) betweensimulation andmeasurement So it shows that the numericalsimulation has good agreement with physical experimentand the methods measuring the permittivity of tires arefeasible
52 Effects of Incident Angle 120579119894on 119879119888 The permittivity of the
test tire is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzfrom Section 51The incident angle 120579
119894is 0∘sim90∘ Amagnitude
of 119879119888for the parallel and perpendicular polarization is shown
in Figure 10
6 International Journal of Antennas and Propagation
0 1 2 3 4 5
001
002
003
004
Absolute error
Frequency (GHz)
Abso
lute
erro
r
Figure 9 Absolute error values
0 11 23 34 45 57 68 79 900
01
02
03
04
05
06
07
Parallel polarizationPerpendicular polarization
Tc
Incident angle 120579i (∘)
Figure 10 Effects of 120579119894on 119879119888
In Figure 10 119879119888for the parallel and perpendicular polar-
ization decreases with increasing incident angle 120579119894 119879119888for the
perpendicular polarization decreases faster than 119879119888for the
parallel polarization This conclusion can be obtained fromthe experiment in Figure 11 The experiment setup containsa reader XC-RF807 and two liner polarization antennae XC-AF26 (one is a horizontal polarization antenna and the otherone is vertical polarization) The carrier frequency of thereader is 866MHz and the power o is 30 dBmWThe gain ofthe antenna is greater than 12 dBi and the frequency range isfrom 840MHz to 868MHz The distance between GL274Atire and reader is 1m and the depth of the tag embed inthe tire is 9mm Figure 12 shows the relation between theidentification rate and angle of incidence
Figure 11 Experiment setup
02
04
06
08
1
Parallel polarizationPerpendicular polarization
0 10 20 30 40 50 60 70 80 900
Iden
tifica
tion
rate
Incidence angle 120579i (∘)
Figure 12 Relations between angle of incidence 120579119894and the identifi-
cation rate
So the parallel polarization and normal incidence arechosen for improving the performance of UHFRFID embed-ded in tires
53 Effects of Distance 119897 on 119879(119891 120579119894 119897) For convenience The
incident angle 120579119894is 0∘ and the permittivity of the test tire
is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzf A magnitude of 119879(119891 120579
119894 119897) for the distance 119897 is shown in
Figure 13In Figure 13 119879(119891 120579
119894 119897) decreases periodically with
increasing the distance 119897 in tires This conclusion canbe obtained from the experiment in Figure 11 In thisexperiment 8 GAL274A tires are used from Guizhou tirelimited company in China When the tires are vulcanizingthe depths of the tag embedded in the tire are 00mm (tag ispasted on the surface of the tire) 30mm 60mm 90mm12mm 15mm 18mm 21mm and 24mm respectively(because of the limitation of the thickness of the tire thebiggest embedded depth is 24mm) Figure 14 shows therelation between the recognition rate and the embeddeddepth 119897 It means the recognition rate of tire embedded RFID
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
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Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
2 International Journal of Antennas and Propagation
FlangeOuter conductor
Dielectric
Coaxial probe
120576lowast
Test materialInner conductor
(a) Measuring system
z
Flange 120588
2a
2b Coa
xial
prob
e
(b) Geometrymodel
Figure 1 Measuring reflection coefficients with open ended coaxialprobe
So this paper focuses on wave propagation for UHFpassive embedded RFID in tires based on the permittivityof tires and tire-air boundary conditions Hence Section 2presents how to measure the permittivity of tires Section 3describes the radio link for UHF RFID systems Section 4gives a propagation model of UHF passive embedded RFIDsystems in car tires Section 5 describes numerical calculationand discussion Section 6 concludes this paper
2 Measuring the Permittivity of Tires
21 Measuring the Permittivity Several techniques have beendeveloped for measuring the permittivity [8ndash10] Howeversome such as resonant cavity or wave-guide transmissionline cells require test hardware machining and destructiveprocessing And open ended coaxial probe (OCP) techniqueis currently one of themost popular techniques formeasuringthe permittivity OCP technique can performnondestructivebroadband (RF andmicrowave bands) and high temperaturemeasurement Its well-developed theory makes it possible toobtain sufficiently accurate results
A schematic for a coaxial open ended probe is shown inFigure 1 To reduce significantlymeasuring error thematerialbeing tested is placed in close contact with the probersquosflat end The reflection coefficient measured with a vectornetwork analyzer (VNA) is used as inverse calculation of thepermittivity of the material
An equivalent circuit of admittance model for a coaxialopen ended probe is shown in Figure 2 In Figure 2 119884
119888is
the probe characteristic admittance and 119884(120596 120576lowast
) is the loadadmittance including the inner admittance 119884
119894(120596) = 119895120596119862
119894
of the capacitance 119862119894between outer conductor and inner
conductor and the outer admittance 119884119900(120596 120576lowast
) obtained bysolving the following equation [11]
119884119900
(120596 120576lowast
) = 11989521205961205760120576lowast
[ln(119887119886)]2∬
119887
119886
int
120587
0
cos120593119890minus119895119896119903
1199031198891205931198891205881015840
119889120588 (1)
where 119896 = 120596radic1205831205761015840 120583 is the permeability 120596 is the oper-ating frequency (120588 120588
1015840
120593) are cylindrical coordinates 119903 =
[1205882
+ 12058810158402
minus 21205881205881015840 cos120593]
12 and 119886 and 119887 are respectively the
YcProbe
Ci 120576lowastC0 1205962(120576lowast)2C2
1205962(120576lowast)15C1
Figure 2 The equivalent circuit of admittance model for a coaxialopen ended probe
interior and the external radius of the probe And (1) can bethe series expansion form of (2)
119884119900
(120596 120576lowast
) =
infin
sum
119899=0
(minus1) (minus119895120596)119899+1
119862119899120576lowast(119899+2)2
(2)
where
119862119899
=2(12058301205760)(119899+2)2
1198991205830[ln(119887119886)]
2∬
119887
119886
int
120587
0
119903119899minus1 cos120593119889120593119889120588
1015840
119889120588 (3)
Equation (3) shows that 119862119899is constant For convenience (2)
can be truncated to 3 terms with the 1198620 1198621 and 119862
2 So
119884(120596 120576lowast
) can be given as below
119884 (120596 120576lowast
) = 119895120596119862119894+ 119895120596120576
lowast
1198620
+ 1205962
(120576lowast
)15
1198621
+ 1198951205963
(120576lowast
)2
1198622
(4)
where 120576lowast
1198620
is the fringing capacitance of the probe1205962
(120576lowast
)2
1198622is the fringing capacitance generated from a
test material and 1205962
(120576lowast
)15
1198621is the equivalent conductance
radiated from the probeThe load admittance 119884(120596 120576
lowast
) can be obtained from theEM wave reflection coefficient Γ(120596 120576
lowast
) using the followingrelation
119884 (120596 120576lowast
) = 119884119888
1 minus Γ (120596 120576lowast
)
1 + Γ (120596 120576lowast) (5)
Hence measuring the permittivity can be performedusing the following steps
Step 1 Using VNA we measure the four different reflectioncoefficients Γ
1 Γ2 Γ3 and Γ
4associated with the four different
frequencies using a standard material with the known per-mittivity Using (4) and (5) the four unknown parameters119862
119894
1198620 1198621 and 119862
2can be solved
Step 2 Using VNA we measure the reflection coefficientsΓ associated with some frequencies using the test materialUsing (4) and (5) the permittivity of the test material can becalculated by a suitable iterative method
22 Measurement Setup for Tires The tire sidewall and theposition of the RFID tag embedded in tire are displayed inFigure 3The tag is embedded parallel to the outer steel mesh
International Journal of Antennas and Propagation 3
Steel
Inner diameterRFID tag
Tire sidewall rubber
Figure 3 The RFID tag embedded in tires
Coaxial cableProbe
Tire specimen
ManipulatorTemperature sensor
VNAAV 3629A
ScrewThermometer
Figure 4 The OCP measurement system
at a distance that depends on the tire size and ranges from 4to 8 cm above the inner steel mesh [1]
To reduce significantly measuring error using OCP tech-nique the tire sidewall specimen has to meet the followingconditions
(i) The surface of the tire sidewall specimen has to be flatA piece of the tire sidewall is cut out and the crosssection is polished to obtain a flat surface
(ii) The specimen has to have semi-infinite thickness sothat the penetration of the fieldmust bemuch smallerthan the specimenrsquos thickness
(iii) There must not be air gaps between probe and the tiresidewall specimen
Figure 4 illustrates an OCP measurement system Thesystem consists of a VNA a thermometer a coaxial probeand a manipulator with screw for fixing the tire sidewallspecimen Tightening the screw the probe is pressed againstthe specimen until no more variation of the measurementresults is observed
23 Simulation Verifying Using HFSS Simulation verifyingusing HFSS to verify the measurement accuracy using OCPtechnique an OCP model using HFSS (high frequency
x
y
z
Air boxPort
Open ended coaxial probe
Tire sidewall material
Figure 5 OCP model based on HFSS
structure simulator) is set up to compare Given themeasuredpermittivity of tire specimen using the measuring methodspresented in Section 21 the reflection coefficient is solvedusing the OCPmodel And the simulation and measurementreflection coefficients are compared
The OCP model based on HFSS is shown in Figure 5In Figure 5 the inner and outer conductors of the probe aremade of gilded brass and the space between the inner andouter conductor is filled in Teflon dielectric material Thetire specimen is modeled as a cylinder To avoid perfectlyconducting boundaries around the tire sidewall material anair box is implemented that surrounds the whole simulationsetup
3 Radio Link for UHF Passive RFID
In passive UHF RFID systems a bidirectional radio link isestablished between reader and tags including a forward linkfrom the reader to tags and a backward link from the tagsto reader What radio link for UHF passive RFID differsfrom conventional radio is that the backward link resemblesradar link Besides the RFID tagrsquos antenna absorbs waves asa function of its load match and reemits waves as a functionof its load mismatch
31 Power Absorbing Coefficient RFID tag consists of anantenna and chip The impedance matching of tag antennaand chip strongly influences the RF power transmissionand the communication performance between reader andtags Because of IC technological limit the impedance of achip cannot be chosen arbitrarily [12] So the chiprsquos inputimpedance is designed to switch between two values betweenthe conjugate impedance called as absorbing impedance119885chip1 and other impedance called as reflecting impedance119885chip2 The quality of the impedance match can be definedby the power absorbing coefficient 120591 which is the poweraccepted by the chip and the available power 119875tag at theantenna port [5 12]
120591 =
4Re [119885ant]Re [119885chip1]
Re [119885ant + 119885chip1]2
+ Im [119885ant + 119885chip1]2 (6)
4 International Journal of Antennas and Propagation
where 119885ant is the tag antennarsquos input impedance and 0 le 120591 le
1 When 120591 = 1 all available power is absorbed by the chipAnd when 120591 = 0 no available power is absorbed by the chipSo the range of frequency that 120591 reaches a demand value isdefined as the bandwidth of the tag antenna This shows thata best designed tag antenna is very important to improve theperformance of UHF passive RFID
32 Power Transmission Coefficient In a passive RFID thepower absorbed by the chip in forward link can be expressedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (7)
where119875TXreader is the transmitted power from reader and119875chipmust be higher than the tagrsquos sensitivity for the tagrsquos normalwork And |119878
21|2 is the power transmitted coefficient in the
forward link depending on the antenna power transmissionof reader and tag (eg antenna gain) and the propagationchannel properties like path loss and fading [5]
The power received by the reader from the tag can beexpressed as in the backward link
119875RXreader =100381610038161003816100381611987812
1003816100381610038161003816
2
120578119875tag =100381610038161003816100381611987812
1003816100381610038161003816
2
120578100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (8)
where 120578 is the modulation efficiency which is defined as theratio of the power scattered by the tag and the power availableat the tag antenna output |119878
12|2 is the power transmitted coef-
ficient in the backward link As real propagation environmentis symmetrical |119878
12|2
= |11987821
|2
4 Model of Power Transmission ofUHF Passive RFID Embedded in Tires
41 Harmonic Waves For time-harmonic fields when themedium presents a conductivity 120590 and permeability 120583 at theoperating frequency 120596 a permittivity 120576
lowast the wave equationcan be written as a time-independent wave equation towards+119911 direction
nabla2
119864 minus 1205742
119864 = 0 (9)
nabla2
119867 minus 1205742
119867 = 0 (10)
minus1205742
= 1198962
(1 minus 119895 tan 120575) = 1205962
120583120576lowast
(11)
where 120576lowast
= 1205761015840
(1 minus 119895 tan 120575) and 119896 = 120596radic1205831205761015840 is the wave numbercorresponding to an unbounded lossless medium with a realdielectric constant 120576
1015840For uniform plane waves nabla
2
= 1205972
1205972
119911 so (9) and(10) have solutions of the form 119864119890
120574119911 and 119867119890120574119911 and the
instantaneous values for the fields are given as follows
= Re 119864119890minus120572119911
119890119895(120596119905minus120573119911)
= Re 119867119890minus120572119911
119890119895(120596119905minus120573119911)
(12)
Free space
R120579i
RFID reader
RFID tag
(a) RFID scenarios in free space
Free space
R120579i
RFID reader RFID tag
Tire
(b) RFID scenarios embedded in tire
Figure 6 RFID scenarios
where the attenuation constant 120572 and the phase constant 120573
can be expressed respectively as follows [13]
120572 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
minus 1]
12
120573 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
+ 1]
12
(13)
So the electric strength decreases with distance 119911 aregiven as
119864 = 1198640119890minus120572119911 cos120573119911 (14)
Substituting (14) into power equation we have
119875 = 1198750
1003816100381610038161003816cos 21205731199111003816100381610038161003816 119890minus2120572119911
(15)
42 Power Transmission for RFID Embedded in Tires TheRFID scenarios in space and embedded in tires are shown inFigure 6 In Figure 6 the incident angle of waves is 120579
119894
In the free space the absorbing power by the RFID tag isgiven as
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
4120587119877)
2
119866119879119875TXreader
(16)
where 120582 is the free space wavelength 119877 is the distance fromRFID reader and 119866
119879is the gain of the tagrsquos antenna
International Journal of Antennas and Propagation 5
In the scenarios embedded in tires (16) can be modifiedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
41205871198771
)
2
10038161003816100381610038161198791198881003816100381610038161003816
2
119866119879
1003816100381610038161003816cos 21205731198971003816100381610038161003816 119890minus2120572119897
119875TXreader
= 120591(120582
41205871198771
)
2
119866119905119879 (119891 120579
119894 119897) 119875TXreader
(17)
where 1198771is the distance between tires and the reader 119879
119888
is electric field transmission coefficient at boundary of tiresand free space and 119879(119891 120579
119894 119897) = |119879
119888|2
| cos 2120573119897|119890minus2120572119897 is power
transmission function depending on 120579119894and the distance 119897 in
tiresWhen a plane EM wave incident at an oblique angle
on tires interface there are two cases to be consideredincident electric field has polarization parallel to the planeof incidence and incident electric field has polarization thatis perpendicular to the plane of incidence So from theboundary conditions that is continuity of tangential electricand magnetic fields at the car tire interface and using theSnellrsquos laws of reflection and refraction the 119879
119888can be derived
as follows
Case 1 Parallel polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119905+ 1205780cos 120579119894
(18)
Case 2 Perpendicular polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119894+ 1205780cos 120579119905
(19)
5 Numerical Analyses
51 Measuring the Permittivity of Tires A standard tire(CPC220555 R16 91V) with the known permittivity (thepermittivity is 120576
1015840
= 35 and tan 120575 = 003 at frequency866MHz) is used to determine the parameters119862
11989411986201198621 and
1198622 Using the measuring methods presented in Section 21
119862119894 1198620 1198621 and 119862
2are 000113 pF 2324 times 10ndash14 pF 1518 times 10ndash
42 pF and 16345 times 10ndash50 pF respectivelyThe measuring results for reflection coefficients in a
Smith chart are shown in Figure 7 using a test car tire (GL274A made in Guizhou Tire Co LTD China) with a vectornetwork analyzer (AV 3629A) between 100MHz and 5GHzat room temperature Using (4) and (5) the permittivity ofthe test car tire can be determined to be 120576
1015840
= 378 andtan 120575 = 0038
Measuring and simulation results can be compared usingthe methods presented in Section 23 In the OCP modelthe inner and outer radiuses of the probe are 065mmand 235mm respectively The thickness of Teflon with arelative permittivity of 120576
1015840 and tan 120575 = 0001 is 135mm Thetest tire is modeled as a cylinder with a radius of 10mmand a height of 10mm The absolute error of the real partof simulation and measuring coefficients and the absolute
90100110120
130
140
150
160
170
180
minus170
minus160
minus150
minus140minus130
minus120
80 7060
50
40
30
20
10
0
minus10
minus20
minus30
minus40
minus50minus60
minus70minus80minus90minus100minus110
000000
020
020
050
050
100
100
200
200
500
500
minus500
minus200
minus020
minus050
minus100
Figure 7 Measured reflection coefficients of a test car tire
00 1 2 3 4 5
001
002
003
004
Absolute error of real partAbsolute error of imaginary part
Frequency (GHz)
Abso
lute
erro
r
Figure 8 Absolute error values of real part and imaginary part
error of the imaginary part of these versus frequency areshown in Figure 8 And the absolute error of the simulationand measuring coefficients is shown in Figure 9 Figures 8and 9 show that there is small deviation (lt0004) betweensimulation andmeasurement So it shows that the numericalsimulation has good agreement with physical experimentand the methods measuring the permittivity of tires arefeasible
52 Effects of Incident Angle 120579119894on 119879119888 The permittivity of the
test tire is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzfrom Section 51The incident angle 120579
119894is 0∘sim90∘ Amagnitude
of 119879119888for the parallel and perpendicular polarization is shown
in Figure 10
6 International Journal of Antennas and Propagation
0 1 2 3 4 5
001
002
003
004
Absolute error
Frequency (GHz)
Abso
lute
erro
r
Figure 9 Absolute error values
0 11 23 34 45 57 68 79 900
01
02
03
04
05
06
07
Parallel polarizationPerpendicular polarization
Tc
Incident angle 120579i (∘)
Figure 10 Effects of 120579119894on 119879119888
In Figure 10 119879119888for the parallel and perpendicular polar-
ization decreases with increasing incident angle 120579119894 119879119888for the
perpendicular polarization decreases faster than 119879119888for the
parallel polarization This conclusion can be obtained fromthe experiment in Figure 11 The experiment setup containsa reader XC-RF807 and two liner polarization antennae XC-AF26 (one is a horizontal polarization antenna and the otherone is vertical polarization) The carrier frequency of thereader is 866MHz and the power o is 30 dBmWThe gain ofthe antenna is greater than 12 dBi and the frequency range isfrom 840MHz to 868MHz The distance between GL274Atire and reader is 1m and the depth of the tag embed inthe tire is 9mm Figure 12 shows the relation between theidentification rate and angle of incidence
Figure 11 Experiment setup
02
04
06
08
1
Parallel polarizationPerpendicular polarization
0 10 20 30 40 50 60 70 80 900
Iden
tifica
tion
rate
Incidence angle 120579i (∘)
Figure 12 Relations between angle of incidence 120579119894and the identifi-
cation rate
So the parallel polarization and normal incidence arechosen for improving the performance of UHFRFID embed-ded in tires
53 Effects of Distance 119897 on 119879(119891 120579119894 119897) For convenience The
incident angle 120579119894is 0∘ and the permittivity of the test tire
is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzf A magnitude of 119879(119891 120579
119894 119897) for the distance 119897 is shown in
Figure 13In Figure 13 119879(119891 120579
119894 119897) decreases periodically with
increasing the distance 119897 in tires This conclusion canbe obtained from the experiment in Figure 11 In thisexperiment 8 GAL274A tires are used from Guizhou tirelimited company in China When the tires are vulcanizingthe depths of the tag embedded in the tire are 00mm (tag ispasted on the surface of the tire) 30mm 60mm 90mm12mm 15mm 18mm 21mm and 24mm respectively(because of the limitation of the thickness of the tire thebiggest embedded depth is 24mm) Figure 14 shows therelation between the recognition rate and the embeddeddepth 119897 It means the recognition rate of tire embedded RFID
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
International Journal of
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Active and Passive Electronic Components
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RotatingMachinery
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Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 3
Steel
Inner diameterRFID tag
Tire sidewall rubber
Figure 3 The RFID tag embedded in tires
Coaxial cableProbe
Tire specimen
ManipulatorTemperature sensor
VNAAV 3629A
ScrewThermometer
Figure 4 The OCP measurement system
at a distance that depends on the tire size and ranges from 4to 8 cm above the inner steel mesh [1]
To reduce significantly measuring error using OCP tech-nique the tire sidewall specimen has to meet the followingconditions
(i) The surface of the tire sidewall specimen has to be flatA piece of the tire sidewall is cut out and the crosssection is polished to obtain a flat surface
(ii) The specimen has to have semi-infinite thickness sothat the penetration of the fieldmust bemuch smallerthan the specimenrsquos thickness
(iii) There must not be air gaps between probe and the tiresidewall specimen
Figure 4 illustrates an OCP measurement system Thesystem consists of a VNA a thermometer a coaxial probeand a manipulator with screw for fixing the tire sidewallspecimen Tightening the screw the probe is pressed againstthe specimen until no more variation of the measurementresults is observed
23 Simulation Verifying Using HFSS Simulation verifyingusing HFSS to verify the measurement accuracy using OCPtechnique an OCP model using HFSS (high frequency
x
y
z
Air boxPort
Open ended coaxial probe
Tire sidewall material
Figure 5 OCP model based on HFSS
structure simulator) is set up to compare Given themeasuredpermittivity of tire specimen using the measuring methodspresented in Section 21 the reflection coefficient is solvedusing the OCPmodel And the simulation and measurementreflection coefficients are compared
The OCP model based on HFSS is shown in Figure 5In Figure 5 the inner and outer conductors of the probe aremade of gilded brass and the space between the inner andouter conductor is filled in Teflon dielectric material Thetire specimen is modeled as a cylinder To avoid perfectlyconducting boundaries around the tire sidewall material anair box is implemented that surrounds the whole simulationsetup
3 Radio Link for UHF Passive RFID
In passive UHF RFID systems a bidirectional radio link isestablished between reader and tags including a forward linkfrom the reader to tags and a backward link from the tagsto reader What radio link for UHF passive RFID differsfrom conventional radio is that the backward link resemblesradar link Besides the RFID tagrsquos antenna absorbs waves asa function of its load match and reemits waves as a functionof its load mismatch
31 Power Absorbing Coefficient RFID tag consists of anantenna and chip The impedance matching of tag antennaand chip strongly influences the RF power transmissionand the communication performance between reader andtags Because of IC technological limit the impedance of achip cannot be chosen arbitrarily [12] So the chiprsquos inputimpedance is designed to switch between two values betweenthe conjugate impedance called as absorbing impedance119885chip1 and other impedance called as reflecting impedance119885chip2 The quality of the impedance match can be definedby the power absorbing coefficient 120591 which is the poweraccepted by the chip and the available power 119875tag at theantenna port [5 12]
120591 =
4Re [119885ant]Re [119885chip1]
Re [119885ant + 119885chip1]2
+ Im [119885ant + 119885chip1]2 (6)
4 International Journal of Antennas and Propagation
where 119885ant is the tag antennarsquos input impedance and 0 le 120591 le
1 When 120591 = 1 all available power is absorbed by the chipAnd when 120591 = 0 no available power is absorbed by the chipSo the range of frequency that 120591 reaches a demand value isdefined as the bandwidth of the tag antenna This shows thata best designed tag antenna is very important to improve theperformance of UHF passive RFID
32 Power Transmission Coefficient In a passive RFID thepower absorbed by the chip in forward link can be expressedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (7)
where119875TXreader is the transmitted power from reader and119875chipmust be higher than the tagrsquos sensitivity for the tagrsquos normalwork And |119878
21|2 is the power transmitted coefficient in the
forward link depending on the antenna power transmissionof reader and tag (eg antenna gain) and the propagationchannel properties like path loss and fading [5]
The power received by the reader from the tag can beexpressed as in the backward link
119875RXreader =100381610038161003816100381611987812
1003816100381610038161003816
2
120578119875tag =100381610038161003816100381611987812
1003816100381610038161003816
2
120578100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (8)
where 120578 is the modulation efficiency which is defined as theratio of the power scattered by the tag and the power availableat the tag antenna output |119878
12|2 is the power transmitted coef-
ficient in the backward link As real propagation environmentis symmetrical |119878
12|2
= |11987821
|2
4 Model of Power Transmission ofUHF Passive RFID Embedded in Tires
41 Harmonic Waves For time-harmonic fields when themedium presents a conductivity 120590 and permeability 120583 at theoperating frequency 120596 a permittivity 120576
lowast the wave equationcan be written as a time-independent wave equation towards+119911 direction
nabla2
119864 minus 1205742
119864 = 0 (9)
nabla2
119867 minus 1205742
119867 = 0 (10)
minus1205742
= 1198962
(1 minus 119895 tan 120575) = 1205962
120583120576lowast
(11)
where 120576lowast
= 1205761015840
(1 minus 119895 tan 120575) and 119896 = 120596radic1205831205761015840 is the wave numbercorresponding to an unbounded lossless medium with a realdielectric constant 120576
1015840For uniform plane waves nabla
2
= 1205972
1205972
119911 so (9) and(10) have solutions of the form 119864119890
120574119911 and 119867119890120574119911 and the
instantaneous values for the fields are given as follows
= Re 119864119890minus120572119911
119890119895(120596119905minus120573119911)
= Re 119867119890minus120572119911
119890119895(120596119905minus120573119911)
(12)
Free space
R120579i
RFID reader
RFID tag
(a) RFID scenarios in free space
Free space
R120579i
RFID reader RFID tag
Tire
(b) RFID scenarios embedded in tire
Figure 6 RFID scenarios
where the attenuation constant 120572 and the phase constant 120573
can be expressed respectively as follows [13]
120572 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
minus 1]
12
120573 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
+ 1]
12
(13)
So the electric strength decreases with distance 119911 aregiven as
119864 = 1198640119890minus120572119911 cos120573119911 (14)
Substituting (14) into power equation we have
119875 = 1198750
1003816100381610038161003816cos 21205731199111003816100381610038161003816 119890minus2120572119911
(15)
42 Power Transmission for RFID Embedded in Tires TheRFID scenarios in space and embedded in tires are shown inFigure 6 In Figure 6 the incident angle of waves is 120579
119894
In the free space the absorbing power by the RFID tag isgiven as
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
4120587119877)
2
119866119879119875TXreader
(16)
where 120582 is the free space wavelength 119877 is the distance fromRFID reader and 119866
119879is the gain of the tagrsquos antenna
International Journal of Antennas and Propagation 5
In the scenarios embedded in tires (16) can be modifiedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
41205871198771
)
2
10038161003816100381610038161198791198881003816100381610038161003816
2
119866119879
1003816100381610038161003816cos 21205731198971003816100381610038161003816 119890minus2120572119897
119875TXreader
= 120591(120582
41205871198771
)
2
119866119905119879 (119891 120579
119894 119897) 119875TXreader
(17)
where 1198771is the distance between tires and the reader 119879
119888
is electric field transmission coefficient at boundary of tiresand free space and 119879(119891 120579
119894 119897) = |119879
119888|2
| cos 2120573119897|119890minus2120572119897 is power
transmission function depending on 120579119894and the distance 119897 in
tiresWhen a plane EM wave incident at an oblique angle
on tires interface there are two cases to be consideredincident electric field has polarization parallel to the planeof incidence and incident electric field has polarization thatis perpendicular to the plane of incidence So from theboundary conditions that is continuity of tangential electricand magnetic fields at the car tire interface and using theSnellrsquos laws of reflection and refraction the 119879
119888can be derived
as follows
Case 1 Parallel polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119905+ 1205780cos 120579119894
(18)
Case 2 Perpendicular polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119894+ 1205780cos 120579119905
(19)
5 Numerical Analyses
51 Measuring the Permittivity of Tires A standard tire(CPC220555 R16 91V) with the known permittivity (thepermittivity is 120576
1015840
= 35 and tan 120575 = 003 at frequency866MHz) is used to determine the parameters119862
11989411986201198621 and
1198622 Using the measuring methods presented in Section 21
119862119894 1198620 1198621 and 119862
2are 000113 pF 2324 times 10ndash14 pF 1518 times 10ndash
42 pF and 16345 times 10ndash50 pF respectivelyThe measuring results for reflection coefficients in a
Smith chart are shown in Figure 7 using a test car tire (GL274A made in Guizhou Tire Co LTD China) with a vectornetwork analyzer (AV 3629A) between 100MHz and 5GHzat room temperature Using (4) and (5) the permittivity ofthe test car tire can be determined to be 120576
1015840
= 378 andtan 120575 = 0038
Measuring and simulation results can be compared usingthe methods presented in Section 23 In the OCP modelthe inner and outer radiuses of the probe are 065mmand 235mm respectively The thickness of Teflon with arelative permittivity of 120576
1015840 and tan 120575 = 0001 is 135mm Thetest tire is modeled as a cylinder with a radius of 10mmand a height of 10mm The absolute error of the real partof simulation and measuring coefficients and the absolute
90100110120
130
140
150
160
170
180
minus170
minus160
minus150
minus140minus130
minus120
80 7060
50
40
30
20
10
0
minus10
minus20
minus30
minus40
minus50minus60
minus70minus80minus90minus100minus110
000000
020
020
050
050
100
100
200
200
500
500
minus500
minus200
minus020
minus050
minus100
Figure 7 Measured reflection coefficients of a test car tire
00 1 2 3 4 5
001
002
003
004
Absolute error of real partAbsolute error of imaginary part
Frequency (GHz)
Abso
lute
erro
r
Figure 8 Absolute error values of real part and imaginary part
error of the imaginary part of these versus frequency areshown in Figure 8 And the absolute error of the simulationand measuring coefficients is shown in Figure 9 Figures 8and 9 show that there is small deviation (lt0004) betweensimulation andmeasurement So it shows that the numericalsimulation has good agreement with physical experimentand the methods measuring the permittivity of tires arefeasible
52 Effects of Incident Angle 120579119894on 119879119888 The permittivity of the
test tire is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzfrom Section 51The incident angle 120579
119894is 0∘sim90∘ Amagnitude
of 119879119888for the parallel and perpendicular polarization is shown
in Figure 10
6 International Journal of Antennas and Propagation
0 1 2 3 4 5
001
002
003
004
Absolute error
Frequency (GHz)
Abso
lute
erro
r
Figure 9 Absolute error values
0 11 23 34 45 57 68 79 900
01
02
03
04
05
06
07
Parallel polarizationPerpendicular polarization
Tc
Incident angle 120579i (∘)
Figure 10 Effects of 120579119894on 119879119888
In Figure 10 119879119888for the parallel and perpendicular polar-
ization decreases with increasing incident angle 120579119894 119879119888for the
perpendicular polarization decreases faster than 119879119888for the
parallel polarization This conclusion can be obtained fromthe experiment in Figure 11 The experiment setup containsa reader XC-RF807 and two liner polarization antennae XC-AF26 (one is a horizontal polarization antenna and the otherone is vertical polarization) The carrier frequency of thereader is 866MHz and the power o is 30 dBmWThe gain ofthe antenna is greater than 12 dBi and the frequency range isfrom 840MHz to 868MHz The distance between GL274Atire and reader is 1m and the depth of the tag embed inthe tire is 9mm Figure 12 shows the relation between theidentification rate and angle of incidence
Figure 11 Experiment setup
02
04
06
08
1
Parallel polarizationPerpendicular polarization
0 10 20 30 40 50 60 70 80 900
Iden
tifica
tion
rate
Incidence angle 120579i (∘)
Figure 12 Relations between angle of incidence 120579119894and the identifi-
cation rate
So the parallel polarization and normal incidence arechosen for improving the performance of UHFRFID embed-ded in tires
53 Effects of Distance 119897 on 119879(119891 120579119894 119897) For convenience The
incident angle 120579119894is 0∘ and the permittivity of the test tire
is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzf A magnitude of 119879(119891 120579
119894 119897) for the distance 119897 is shown in
Figure 13In Figure 13 119879(119891 120579
119894 119897) decreases periodically with
increasing the distance 119897 in tires This conclusion canbe obtained from the experiment in Figure 11 In thisexperiment 8 GAL274A tires are used from Guizhou tirelimited company in China When the tires are vulcanizingthe depths of the tag embedded in the tire are 00mm (tag ispasted on the surface of the tire) 30mm 60mm 90mm12mm 15mm 18mm 21mm and 24mm respectively(because of the limitation of the thickness of the tire thebiggest embedded depth is 24mm) Figure 14 shows therelation between the recognition rate and the embeddeddepth 119897 It means the recognition rate of tire embedded RFID
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
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International Journal of
4 International Journal of Antennas and Propagation
where 119885ant is the tag antennarsquos input impedance and 0 le 120591 le
1 When 120591 = 1 all available power is absorbed by the chipAnd when 120591 = 0 no available power is absorbed by the chipSo the range of frequency that 120591 reaches a demand value isdefined as the bandwidth of the tag antenna This shows thata best designed tag antenna is very important to improve theperformance of UHF passive RFID
32 Power Transmission Coefficient In a passive RFID thepower absorbed by the chip in forward link can be expressedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (7)
where119875TXreader is the transmitted power from reader and119875chipmust be higher than the tagrsquos sensitivity for the tagrsquos normalwork And |119878
21|2 is the power transmitted coefficient in the
forward link depending on the antenna power transmissionof reader and tag (eg antenna gain) and the propagationchannel properties like path loss and fading [5]
The power received by the reader from the tag can beexpressed as in the backward link
119875RXreader =100381610038161003816100381611987812
1003816100381610038161003816
2
120578119875tag =100381610038161003816100381611987812
1003816100381610038161003816
2
120578100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader (8)
where 120578 is the modulation efficiency which is defined as theratio of the power scattered by the tag and the power availableat the tag antenna output |119878
12|2 is the power transmitted coef-
ficient in the backward link As real propagation environmentis symmetrical |119878
12|2
= |11987821
|2
4 Model of Power Transmission ofUHF Passive RFID Embedded in Tires
41 Harmonic Waves For time-harmonic fields when themedium presents a conductivity 120590 and permeability 120583 at theoperating frequency 120596 a permittivity 120576
lowast the wave equationcan be written as a time-independent wave equation towards+119911 direction
nabla2
119864 minus 1205742
119864 = 0 (9)
nabla2
119867 minus 1205742
119867 = 0 (10)
minus1205742
= 1198962
(1 minus 119895 tan 120575) = 1205962
120583120576lowast
(11)
where 120576lowast
= 1205761015840
(1 minus 119895 tan 120575) and 119896 = 120596radic1205831205761015840 is the wave numbercorresponding to an unbounded lossless medium with a realdielectric constant 120576
1015840For uniform plane waves nabla
2
= 1205972
1205972
119911 so (9) and(10) have solutions of the form 119864119890
120574119911 and 119867119890120574119911 and the
instantaneous values for the fields are given as follows
= Re 119864119890minus120572119911
119890119895(120596119905minus120573119911)
= Re 119867119890minus120572119911
119890119895(120596119905minus120573119911)
(12)
Free space
R120579i
RFID reader
RFID tag
(a) RFID scenarios in free space
Free space
R120579i
RFID reader RFID tag
Tire
(b) RFID scenarios embedded in tire
Figure 6 RFID scenarios
where the attenuation constant 120572 and the phase constant 120573
can be expressed respectively as follows [13]
120572 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
minus 1]
12
120573 = 120596(1205831205761015840
2)
12
[(1 + tan2120575)12
+ 1]
12
(13)
So the electric strength decreases with distance 119911 aregiven as
119864 = 1198640119890minus120572119911 cos120573119911 (14)
Substituting (14) into power equation we have
119875 = 1198750
1003816100381610038161003816cos 21205731199111003816100381610038161003816 119890minus2120572119911
(15)
42 Power Transmission for RFID Embedded in Tires TheRFID scenarios in space and embedded in tires are shown inFigure 6 In Figure 6 the incident angle of waves is 120579
119894
In the free space the absorbing power by the RFID tag isgiven as
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
4120587119877)
2
119866119879119875TXreader
(16)
where 120582 is the free space wavelength 119877 is the distance fromRFID reader and 119866
119879is the gain of the tagrsquos antenna
International Journal of Antennas and Propagation 5
In the scenarios embedded in tires (16) can be modifiedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
41205871198771
)
2
10038161003816100381610038161198791198881003816100381610038161003816
2
119866119879
1003816100381610038161003816cos 21205731198971003816100381610038161003816 119890minus2120572119897
119875TXreader
= 120591(120582
41205871198771
)
2
119866119905119879 (119891 120579
119894 119897) 119875TXreader
(17)
where 1198771is the distance between tires and the reader 119879
119888
is electric field transmission coefficient at boundary of tiresand free space and 119879(119891 120579
119894 119897) = |119879
119888|2
| cos 2120573119897|119890minus2120572119897 is power
transmission function depending on 120579119894and the distance 119897 in
tiresWhen a plane EM wave incident at an oblique angle
on tires interface there are two cases to be consideredincident electric field has polarization parallel to the planeof incidence and incident electric field has polarization thatis perpendicular to the plane of incidence So from theboundary conditions that is continuity of tangential electricand magnetic fields at the car tire interface and using theSnellrsquos laws of reflection and refraction the 119879
119888can be derived
as follows
Case 1 Parallel polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119905+ 1205780cos 120579119894
(18)
Case 2 Perpendicular polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119894+ 1205780cos 120579119905
(19)
5 Numerical Analyses
51 Measuring the Permittivity of Tires A standard tire(CPC220555 R16 91V) with the known permittivity (thepermittivity is 120576
1015840
= 35 and tan 120575 = 003 at frequency866MHz) is used to determine the parameters119862
11989411986201198621 and
1198622 Using the measuring methods presented in Section 21
119862119894 1198620 1198621 and 119862
2are 000113 pF 2324 times 10ndash14 pF 1518 times 10ndash
42 pF and 16345 times 10ndash50 pF respectivelyThe measuring results for reflection coefficients in a
Smith chart are shown in Figure 7 using a test car tire (GL274A made in Guizhou Tire Co LTD China) with a vectornetwork analyzer (AV 3629A) between 100MHz and 5GHzat room temperature Using (4) and (5) the permittivity ofthe test car tire can be determined to be 120576
1015840
= 378 andtan 120575 = 0038
Measuring and simulation results can be compared usingthe methods presented in Section 23 In the OCP modelthe inner and outer radiuses of the probe are 065mmand 235mm respectively The thickness of Teflon with arelative permittivity of 120576
1015840 and tan 120575 = 0001 is 135mm Thetest tire is modeled as a cylinder with a radius of 10mmand a height of 10mm The absolute error of the real partof simulation and measuring coefficients and the absolute
90100110120
130
140
150
160
170
180
minus170
minus160
minus150
minus140minus130
minus120
80 7060
50
40
30
20
10
0
minus10
minus20
minus30
minus40
minus50minus60
minus70minus80minus90minus100minus110
000000
020
020
050
050
100
100
200
200
500
500
minus500
minus200
minus020
minus050
minus100
Figure 7 Measured reflection coefficients of a test car tire
00 1 2 3 4 5
001
002
003
004
Absolute error of real partAbsolute error of imaginary part
Frequency (GHz)
Abso
lute
erro
r
Figure 8 Absolute error values of real part and imaginary part
error of the imaginary part of these versus frequency areshown in Figure 8 And the absolute error of the simulationand measuring coefficients is shown in Figure 9 Figures 8and 9 show that there is small deviation (lt0004) betweensimulation andmeasurement So it shows that the numericalsimulation has good agreement with physical experimentand the methods measuring the permittivity of tires arefeasible
52 Effects of Incident Angle 120579119894on 119879119888 The permittivity of the
test tire is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzfrom Section 51The incident angle 120579
119894is 0∘sim90∘ Amagnitude
of 119879119888for the parallel and perpendicular polarization is shown
in Figure 10
6 International Journal of Antennas and Propagation
0 1 2 3 4 5
001
002
003
004
Absolute error
Frequency (GHz)
Abso
lute
erro
r
Figure 9 Absolute error values
0 11 23 34 45 57 68 79 900
01
02
03
04
05
06
07
Parallel polarizationPerpendicular polarization
Tc
Incident angle 120579i (∘)
Figure 10 Effects of 120579119894on 119879119888
In Figure 10 119879119888for the parallel and perpendicular polar-
ization decreases with increasing incident angle 120579119894 119879119888for the
perpendicular polarization decreases faster than 119879119888for the
parallel polarization This conclusion can be obtained fromthe experiment in Figure 11 The experiment setup containsa reader XC-RF807 and two liner polarization antennae XC-AF26 (one is a horizontal polarization antenna and the otherone is vertical polarization) The carrier frequency of thereader is 866MHz and the power o is 30 dBmWThe gain ofthe antenna is greater than 12 dBi and the frequency range isfrom 840MHz to 868MHz The distance between GL274Atire and reader is 1m and the depth of the tag embed inthe tire is 9mm Figure 12 shows the relation between theidentification rate and angle of incidence
Figure 11 Experiment setup
02
04
06
08
1
Parallel polarizationPerpendicular polarization
0 10 20 30 40 50 60 70 80 900
Iden
tifica
tion
rate
Incidence angle 120579i (∘)
Figure 12 Relations between angle of incidence 120579119894and the identifi-
cation rate
So the parallel polarization and normal incidence arechosen for improving the performance of UHFRFID embed-ded in tires
53 Effects of Distance 119897 on 119879(119891 120579119894 119897) For convenience The
incident angle 120579119894is 0∘ and the permittivity of the test tire
is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzf A magnitude of 119879(119891 120579
119894 119897) for the distance 119897 is shown in
Figure 13In Figure 13 119879(119891 120579
119894 119897) decreases periodically with
increasing the distance 119897 in tires This conclusion canbe obtained from the experiment in Figure 11 In thisexperiment 8 GAL274A tires are used from Guizhou tirelimited company in China When the tires are vulcanizingthe depths of the tag embedded in the tire are 00mm (tag ispasted on the surface of the tire) 30mm 60mm 90mm12mm 15mm 18mm 21mm and 24mm respectively(because of the limitation of the thickness of the tire thebiggest embedded depth is 24mm) Figure 14 shows therelation between the recognition rate and the embeddeddepth 119897 It means the recognition rate of tire embedded RFID
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 5
In the scenarios embedded in tires (16) can be modifiedas
119875chip = 120591119875tag = 120591100381610038161003816100381611987821
1003816100381610038161003816
2
119875TXreader
= 120591(120582
41205871198771
)
2
10038161003816100381610038161198791198881003816100381610038161003816
2
119866119879
1003816100381610038161003816cos 21205731198971003816100381610038161003816 119890minus2120572119897
119875TXreader
= 120591(120582
41205871198771
)
2
119866119905119879 (119891 120579
119894 119897) 119875TXreader
(17)
where 1198771is the distance between tires and the reader 119879
119888
is electric field transmission coefficient at boundary of tiresand free space and 119879(119891 120579
119894 119897) = |119879
119888|2
| cos 2120573119897|119890minus2120572119897 is power
transmission function depending on 120579119894and the distance 119897 in
tiresWhen a plane EM wave incident at an oblique angle
on tires interface there are two cases to be consideredincident electric field has polarization parallel to the planeof incidence and incident electric field has polarization thatis perpendicular to the plane of incidence So from theboundary conditions that is continuity of tangential electricand magnetic fields at the car tire interface and using theSnellrsquos laws of reflection and refraction the 119879
119888can be derived
as follows
Case 1 Parallel polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119905+ 1205780cos 120579119894
(18)
Case 2 Perpendicular polarization
119879119888
=21205781cos 120579119894
1205781cos 120579119894+ 1205780cos 120579119905
(19)
5 Numerical Analyses
51 Measuring the Permittivity of Tires A standard tire(CPC220555 R16 91V) with the known permittivity (thepermittivity is 120576
1015840
= 35 and tan 120575 = 003 at frequency866MHz) is used to determine the parameters119862
11989411986201198621 and
1198622 Using the measuring methods presented in Section 21
119862119894 1198620 1198621 and 119862
2are 000113 pF 2324 times 10ndash14 pF 1518 times 10ndash
42 pF and 16345 times 10ndash50 pF respectivelyThe measuring results for reflection coefficients in a
Smith chart are shown in Figure 7 using a test car tire (GL274A made in Guizhou Tire Co LTD China) with a vectornetwork analyzer (AV 3629A) between 100MHz and 5GHzat room temperature Using (4) and (5) the permittivity ofthe test car tire can be determined to be 120576
1015840
= 378 andtan 120575 = 0038
Measuring and simulation results can be compared usingthe methods presented in Section 23 In the OCP modelthe inner and outer radiuses of the probe are 065mmand 235mm respectively The thickness of Teflon with arelative permittivity of 120576
1015840 and tan 120575 = 0001 is 135mm Thetest tire is modeled as a cylinder with a radius of 10mmand a height of 10mm The absolute error of the real partof simulation and measuring coefficients and the absolute
90100110120
130
140
150
160
170
180
minus170
minus160
minus150
minus140minus130
minus120
80 7060
50
40
30
20
10
0
minus10
minus20
minus30
minus40
minus50minus60
minus70minus80minus90minus100minus110
000000
020
020
050
050
100
100
200
200
500
500
minus500
minus200
minus020
minus050
minus100
Figure 7 Measured reflection coefficients of a test car tire
00 1 2 3 4 5
001
002
003
004
Absolute error of real partAbsolute error of imaginary part
Frequency (GHz)
Abso
lute
erro
r
Figure 8 Absolute error values of real part and imaginary part
error of the imaginary part of these versus frequency areshown in Figure 8 And the absolute error of the simulationand measuring coefficients is shown in Figure 9 Figures 8and 9 show that there is small deviation (lt0004) betweensimulation andmeasurement So it shows that the numericalsimulation has good agreement with physical experimentand the methods measuring the permittivity of tires arefeasible
52 Effects of Incident Angle 120579119894on 119879119888 The permittivity of the
test tire is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzfrom Section 51The incident angle 120579
119894is 0∘sim90∘ Amagnitude
of 119879119888for the parallel and perpendicular polarization is shown
in Figure 10
6 International Journal of Antennas and Propagation
0 1 2 3 4 5
001
002
003
004
Absolute error
Frequency (GHz)
Abso
lute
erro
r
Figure 9 Absolute error values
0 11 23 34 45 57 68 79 900
01
02
03
04
05
06
07
Parallel polarizationPerpendicular polarization
Tc
Incident angle 120579i (∘)
Figure 10 Effects of 120579119894on 119879119888
In Figure 10 119879119888for the parallel and perpendicular polar-
ization decreases with increasing incident angle 120579119894 119879119888for the
perpendicular polarization decreases faster than 119879119888for the
parallel polarization This conclusion can be obtained fromthe experiment in Figure 11 The experiment setup containsa reader XC-RF807 and two liner polarization antennae XC-AF26 (one is a horizontal polarization antenna and the otherone is vertical polarization) The carrier frequency of thereader is 866MHz and the power o is 30 dBmWThe gain ofthe antenna is greater than 12 dBi and the frequency range isfrom 840MHz to 868MHz The distance between GL274Atire and reader is 1m and the depth of the tag embed inthe tire is 9mm Figure 12 shows the relation between theidentification rate and angle of incidence
Figure 11 Experiment setup
02
04
06
08
1
Parallel polarizationPerpendicular polarization
0 10 20 30 40 50 60 70 80 900
Iden
tifica
tion
rate
Incidence angle 120579i (∘)
Figure 12 Relations between angle of incidence 120579119894and the identifi-
cation rate
So the parallel polarization and normal incidence arechosen for improving the performance of UHFRFID embed-ded in tires
53 Effects of Distance 119897 on 119879(119891 120579119894 119897) For convenience The
incident angle 120579119894is 0∘ and the permittivity of the test tire
is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzf A magnitude of 119879(119891 120579
119894 119897) for the distance 119897 is shown in
Figure 13In Figure 13 119879(119891 120579
119894 119897) decreases periodically with
increasing the distance 119897 in tires This conclusion canbe obtained from the experiment in Figure 11 In thisexperiment 8 GAL274A tires are used from Guizhou tirelimited company in China When the tires are vulcanizingthe depths of the tag embedded in the tire are 00mm (tag ispasted on the surface of the tire) 30mm 60mm 90mm12mm 15mm 18mm 21mm and 24mm respectively(because of the limitation of the thickness of the tire thebiggest embedded depth is 24mm) Figure 14 shows therelation between the recognition rate and the embeddeddepth 119897 It means the recognition rate of tire embedded RFID
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
6 International Journal of Antennas and Propagation
0 1 2 3 4 5
001
002
003
004
Absolute error
Frequency (GHz)
Abso
lute
erro
r
Figure 9 Absolute error values
0 11 23 34 45 57 68 79 900
01
02
03
04
05
06
07
Parallel polarizationPerpendicular polarization
Tc
Incident angle 120579i (∘)
Figure 10 Effects of 120579119894on 119879119888
In Figure 10 119879119888for the parallel and perpendicular polar-
ization decreases with increasing incident angle 120579119894 119879119888for the
perpendicular polarization decreases faster than 119879119888for the
parallel polarization This conclusion can be obtained fromthe experiment in Figure 11 The experiment setup containsa reader XC-RF807 and two liner polarization antennae XC-AF26 (one is a horizontal polarization antenna and the otherone is vertical polarization) The carrier frequency of thereader is 866MHz and the power o is 30 dBmWThe gain ofthe antenna is greater than 12 dBi and the frequency range isfrom 840MHz to 868MHz The distance between GL274Atire and reader is 1m and the depth of the tag embed inthe tire is 9mm Figure 12 shows the relation between theidentification rate and angle of incidence
Figure 11 Experiment setup
02
04
06
08
1
Parallel polarizationPerpendicular polarization
0 10 20 30 40 50 60 70 80 900
Iden
tifica
tion
rate
Incidence angle 120579i (∘)
Figure 12 Relations between angle of incidence 120579119894and the identifi-
cation rate
So the parallel polarization and normal incidence arechosen for improving the performance of UHFRFID embed-ded in tires
53 Effects of Distance 119897 on 119879(119891 120579119894 119897) For convenience The
incident angle 120579119894is 0∘ and the permittivity of the test tire
is 1205761015840
= 378 and tan 120575 = 0038 at frequency 866MHzf A magnitude of 119879(119891 120579
119894 119897) for the distance 119897 is shown in
Figure 13In Figure 13 119879(119891 120579
119894 119897) decreases periodically with
increasing the distance 119897 in tires This conclusion canbe obtained from the experiment in Figure 11 In thisexperiment 8 GAL274A tires are used from Guizhou tirelimited company in China When the tires are vulcanizingthe depths of the tag embedded in the tire are 00mm (tag ispasted on the surface of the tire) 30mm 60mm 90mm12mm 15mm 18mm 21mm and 24mm respectively(because of the limitation of the thickness of the tire thebiggest embedded depth is 24mm) Figure 14 shows therelation between the recognition rate and the embeddeddepth 119897 It means the recognition rate of tire embedded RFID
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of Antennas and Propagation 7
0 005 01 015 02 025 03 035 040
005
01
015
02
025
03
035
Pow
er tr
ansm
issio
n fu
nctio
n
Distance l (cm) in tires
Figure 13 Effects of 119897 on119879(119891 120579119894 119897)
0 5 10 15 20 25 30
02
04
06
08
1
11
Iden
tifica
tion
rate
Distance l (mm) in tires
Figure 14 Relations 119897 and identification rate
system declines along with 119897 also fluctuates along with 119897This means the power transmission of tire embedded RFIDsystem declines along with 119897 also fluctuates along with 119897
So the distance 119897 is chosen to keep119879(119891 120579119894 119897) from locating
valley
6 Conclusions
From now on UHF RFID tags embedded in tires have a deepimpact on tire life cycle management and tire monitoring Sowe present the power transmission of wave propagation forUHF embedded RFID in tires
In UHF passive embedded RFID systems in tires thebidirectional radio link between reader and tags goes throughair and tiresThe total path loss contains reflection loss at tire-air boundaries So we give the OCP method for measuringthe permittivity of tires By analyzing the radio link for UHFpassive RFID we establish a model of wave propagation of
UHF embedded RFID in tires and make numerical analysesFinally we make the conclusion as follows
(i) The error of the OCP methods for measuring thepermittivity of tires is small And the methods canbe used in measuring the permittivity of tires fordesigning the UHF embedded RFID in tires
(ii) It is necessary to optimize and design the antenna oftag for the impedance matching of tag antenna andchip This can improve the performance of the UHFembedded RFID in tires
(iii) The parallel polarization and normal incidence arechosen for improving the performance of the UHFembedded RFID in tires Finally the distance 119897 ischosen to keep 119879(119891 120579
119894 119897) from locating valley
Conflict of Interests
The authors declare that they have no financial and personalrelationships with other people or organizations that caninappropriately influence their work there is no professionalor other personal interests of any nature or kind in anyproduct service andor company that could be construed asinfluencing the position presented in this paper
Acknowledgments
The authors wish to thank the editor and reviewers for theirvaluable comments corrections and suggestions which ledto an improved version of the original paper This researchis a project partially supported by the Guizhou Natural Sci-ence Foundation (Grant no 2012[38]) the National NaturalScience Foundation of China (Grant no 61362004) andGuizhou Science andTechnology InnovationGroup forRFIDampWSN
References
[1] S Basat K Lim I Kim M M Tentzeris and J Laskar ldquoDesignand development of a miniaturized embedded UHF RFID tagfor automotive tire applicationsrdquo in Proceedings of the 55thElectronic Components and Technology Conference (ECTC rsquo05)pp 867ndash870 Lake Buena Vista Fla USA June 2005
[2] RFID 24-7 USA ldquoMichelin rolls out RFID-enabled tires forLondon Olympicrdquo 1 pages 2012 httpwwwrfid24-7comarticlemichelin-rolls-out-rfid-enabled-tires-for-london-olym-pics
[3] RFID Journal USA ldquoMichelin embeds RFID tags in tiresrdquo 2pages 2012 httpwwwrfidjournalcomarticleview26911
[4] RFID Journal USA ldquoRFID chip to monitor tire pressurerdquo 2pages 2012 httpwwwrfidjournalcomarticleview9311
[5] J D Griffin and G D Durgin ldquoComplete link budgets forbackscatter-radio and RFID systemsrdquo IEEE Antennas and Prop-agation Magazine vol 51 no 2 pp 11ndash25 2009
[6] P V Nikitin and K V S Rao ldquoAntennas and propagation inUHF RFID systemsrdquo in Proceedings of the IEEE InternationalConference on RFID (IEEE RFID rsquo08) pp 277ndash288 Las VegasNev USA April 2008
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
8 International Journal of Antennas and Propagation
[7] P V Nikitin and K V S Rao ldquoTheory and measurement ofbackscattering from RFID tagsrdquo IEEE Antennas and Propaga-tion Magazine vol 48 no 6 pp 212ndash218 2006
[8] V Komarov S Wang and J Tang ldquoPermittivity and mea-surementrdquo in The Wiley Encyclopedia of RF and MicrowaveEngineering vol 4 pp 3693ndash3711 2005
[9] C C Courtney ldquoTime-domain measurement of the elec-tromagnetic properties of materialsrdquo IEEE Transactions onMicrowave Theory and Techniques vol 46 no 5 pp 517ndash5221998
[10] S Jing D Ding and Q Jing ldquoMeasurement of electromagneticproperties of materials using transmissionreflectionmethod incoaxial linerdquo in Proceedings of the 3rd Asia Pacific Conference onEnvironmental Electromagnetics pp 129ndash135Hangzhou China2003
[11] D K Misra ldquoA quasi-static analysis of open-ended coaxiallinesrdquo IEEE Transactions on Microwave Theory and Techniquesvol 35 no 10 pp 925ndash928 1988
[12] J Grosinger and A L Scholtz ldquoAntennas and wave propagationin novel wireless sensing applications based on passive UHFRFIDrdquo Elektrotechnik und Informationstechnik vol 128 no 11-12 pp 408ndash414 2011
[13] A V Hippel Dielectrics and Waves John Wiley amp Sons NewYork NY USA 1954
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
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