A Printed Rampart-Line Antenna with a Dielectric Superstrate for UHF RFID Applications Benjamin D....

A Printed Rampart-Line Antenna with a A Printed Rampart-Line Antenna with a Dielectric Superstrate for UHF RFID Dielectric Superstrate for UHF RFID

ApplicationsApplications

Benjamin D. BraatenBenjamin D. BraatenGregory J. OwenGregory J. OwenDustin VaselaarDustin VaselaarRobert M. NelsonRobert M. Nelson

Cherish Bauer-ReichCherish Bauer-ReichJacob GlowerJacob GlowerBrian Morlock (PacketDigital LLC)Brian Morlock (PacketDigital LLC)Michael Reich (CNSE)Michael Reich (CNSE)Aaron Reinholz (CNSE)Aaron Reinholz (CNSE)

North Dakota State UniversityNorth Dakota State University

TopicsTopics

IntroductionIntroduction BackgroundBackground Design ProcessDesign Process Design ExampleDesign Example ConclusionConclusion


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]

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



Our work focused on the antenna design of a passive Our work focused on the antenna design of a passive RFID tag.RFID tag.

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]: Isotropic and anisotropic superstratesIsotropic and anisotropic superstrates Surface placement of tagSurface placement of tag Other RFID tagsOther RFID tags



Several advantages are Several advantages are gained by using a gained by using a superstrate [18]:superstrate [18]: Protection against heat, Protection against heat,

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

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


BackgroundBackground

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


BackgroundBackground

The layout region can contain many different The layout region can contain many different designs and be located on many different designs and be located on many different surfaces [27]-[38]:surfaces [27]-[38]:


Antenna Design ProcessAntenna Design Process

First start with determining the electrical First start with determining the electrical length of each segment of a rampart line length of each segment of a rampart line antenna.antenna.



The length of the kth The length of the kth segment is written segment is written as:as:

This then gives the This then gives the entire length of the entire length of the dipole as:dipole as:


For the rest of this For the rest of this paper we assumed paper we assumed the following the following symmetry:symmetry:

Same length

Same length



Next, start with the rampart line antenna and use Next, start with the rampart line antenna and use a CAD program to determine N:a CAD program to determine N:

Design forDesign for

the applicationthe application

Located here


Then define pivot points to fit the antenna on Then define pivot points to fit the antenna on the space provided and define an the space provided and define an inductive loop for input impedance:inductive loop for input impedance:

Antenna Design ResultsAntenna Design Results

Operating frequency of 920MHzOperating frequency of 920MHz 60mil substrate with permittivity of 4.2560mil substrate with permittivity of 4.25 60mil superstrate with permittivity of 4.060mil superstrate with permittivity of 4.0 Results in N=12Results in N=12 Gr=4.3dBiGr=4.3dBi



Layout a): (H=2985mils and W=1522mils)Layout a): (H=2985mils and W=1522mils) Gr=2.62dBiGr=2.62dBi Zin=10.527+j139.263Zin=10.527+j139.263

Layout b): (H=2746mils and W=1540mils)Layout b): (H=2746mils and W=1540mils) Gr=2.97dBiGr=2.97dBi Zin=36.93+j139.737Zin=36.93+j139.737


The printed boards The printed boards on 5mil FR4 and BT on 5mil FR4 and BT substrate, resp.substrate, resp.

Type F and Type Type F and Type PFC epoxy was used PFC epoxy was used to attach strapsto attach straps

Cured at 50C for Cured at 50C for 8hrs.8hrs.

Both layouts with Both layouts with both substrates and both substrates and epoxy were tested.epoxy were tested.


Measurement ResultsMeasurement Results

The test structureThe test structure


The read range resultsThe read range results


Several normalized-pattern resultsSeveral normalized-pattern results

Etheta Ephi


Simulated gain and input impedance results:Simulated gain and input impedance results:


ConclusionConclusion

A design process based on a Rampart line antenna A design process based on a Rampart line antenna has been presentedhas been presented

Yields antennas with:Yields antennas with: high gain, high gain, flexible impedance values, flexible impedance values, high space filling and high space filling and constant impedanceconstant impedance

Two designs have been validated with measurement Two designs have been validated with measurement and shows to yield a comparable read range to tags and shows to yield a comparable read range to tags applied to other applications.applied to other applications.


QuestionsQuestions

Thank you for listeningThank you for listening


ReferencesReferences

A Printed Rampart-Line Antenna with a Dielectric Superstrate for UHF RFID Applications Benjamin D....

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