On The Effect of Mutual Coupling on LF and On The Effect of Mutual Coupling on LF and UHF Tags Implemented in Dual Frequency UHF Tags Implemented in Dual Frequency

RFID ApplicationsRFID Applications

Gregory J. OwenGregory J. OwenBenjamin D. Braaten*Benjamin D. Braaten*Robert M. NelsonRobert M. NelsonDustin VaselaarDustin Vaselaar

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Cherish Bauer-ReichCherish Bauer-ReichJacob GlowerJacob GlowerMichael ReichMichael ReichAaron ReinholzAaron Reinholz

TopicsTopics

IntroductionIntroduction Dual frequency tagDual frequency tag Test setupTest setup Test resultsTest results DiscussionDiscussion ConclusionConclusion

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IntroductionIntroduction

Interest in RFID has recently grown Interest in RFID has recently grown tremendously in many areas [1]-[5]:tremendously in many areas [1]-[5]: supply chain management [6]-[8]supply chain management [6]-[8] RFID security [9]-[10]RFID security [9]-[10] UHF antenna design [11]UHF antenna design [11] back-scattering analysis [12]-[14]back-scattering analysis [12]-[14] dual frequency applicationsdual frequency applications

Types of systems [1]Types of systems [1] passivepassive semi-passivesemi-passive activeactive

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IntroductionIntroduction

On a passive tag the antenna is typically connected On a passive tag the antenna is typically connected directly to the rectifier.directly to the rectifier. thus antenna impedance and rectifier impedance thus antenna impedance and rectifier impedance

directly effect the read rangedirectly effect the read range Antenna characteristics (gain, input impedance and Antenna characteristics (gain, input impedance and

resonant frequency) can be effected by nearby resonant frequency) can be effected by nearby conducting and non-conducting objects [15]-[21]:conducting and non-conducting objects [15]-[21]: Weather-proof enclosuresWeather-proof enclosures Surface placement of tagSurface placement of tag Other RFID tags (i.e., dual-frequency tags)Other RFID tags (i.e., dual-frequency tags)

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IntroductionIntroduction

Several advantages are Several advantages are gained by using a gained by using a weather-proof enclosure weather-proof enclosure [18]:[18]: Protection against heat, Protection against heat,

physical damage, and the physical damage, and the environment (moisture, sun)environment (moisture, sun)

Dual-frequency Dual-frequency implementationimplementation

Several examples include:Several examples include: Electronic car tolling [22]Electronic car tolling [22] Livestock tracking [23]-[24]Livestock tracking [23]-[24]

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A Little BackgroundA Little Background

The max theoretical read range of a passive The max theoretical read range of a passive RFID tag can be written as (using Friis’s eqn.) RFID tag can be written as (using Friis’s eqn.) [25]:[25]:

wherewhere

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The Dual-Frequency Tag and Test The Dual-Frequency Tag and Test SetupSetup

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(902-928MHz) (125.4-134kHz)

Test SetupTest Setup

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Test ResultsTest Results

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(reminder)

LF tag

Test ResultsTest Results

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(reminder)

M-tag [33]

Test ResultsTest Results

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(reminder)

SquiggleTag [33]

Test ResultsTest Results

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(reminder)

Rampart tag [29]

DiscussionDiscussion

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Table 3 showed that a LF tag placed Table 3 showed that a LF tag placed directly on the M-tag reduced the read directly on the M-tag reduced the read range by 67.27%.range by 67.27%.

Table 4 showed that the LF tag placed Table 4 showed that the LF tag placed near the squiggle tag reduced the read near the squiggle tag reduced the read range by 91.84%.range by 91.84%.

The Rampart-line was less affected by the The Rampart-line was less affected by the LF tag.LF tag.

DiscussionDiscussion

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In all cases by moving the LF tag to the In all cases by moving the LF tag to the edge of the UHF tags the read range could edge of the UHF tags the read range could be recovered.be recovered.

The trade-off to moving the LF tag to the The trade-off to moving the LF tag to the edge of the UHF tag is a larger footprint.edge of the UHF tag is a larger footprint.

ConclusionConclusion

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A dual frequency (UHF and LF) tag has A dual frequency (UHF and LF) tag has been introduced.been introduced.

The read range of each tag was The read range of each tag was determined in the presence of mutual determined in the presence of mutual coupling.coupling.

In several instances the read range of the In several instances the read range of the UHF tag was substantially decreased UHF tag was substantially decreased (91.84%).(91.84%).

ConclusionConclusion

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In all instances is was shown that most of In all instances is was shown that most of the read range could be recovered by the read range could be recovered by moving the LF tag to the same plane of moving the LF tag to the same plane of the UHF tagthe UHF tag

QuestionsQuestions

Thank you for listeningThank you for listening

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ReferencesReferences

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