platform-tolerant rfid tag antenna
DESCRIPTION
TRANSCRIPT
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Platform-Tolerant RFID Tag Antenna
Y. C. Or (1), K. W. Leung *(1) , R. Mittra(2), and K.V.S. Rao(3)
(1). Wireless Communications Research Centre and Department of Electronic Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong.
E-mail: [email protected] E-mail: [email protected]
(2). EE Department, Pennsylvania State University, 319 Electrical Engineering East University Park, PA 16802-2705
E-mail: [email protected]
(3). RFID Intellitag Engineering Department, Intermec Technologies Corporation, Everett, WA 98203 USA
E-mail: [email protected]
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Outline
1. Introduction
2. OR-Patch Antenna
3. RFID Tag Antenna
4. Conclusion
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Objectives
Design an OR-shaped patch antenna.
Design a platform-tolerant RFID tag antenna with the patch antenna (902-928 MHz).
Measure the read range of the tag antenna.
Test the platform-tolerant ability.
Introduction
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Impedance MatchingIntroduction
Thevenin's equivalent circuit of an RFID tag
Circuit Model of an RFID Tag
where Ra and Rc are the input resistances of the tag antenna and of the chip, respectively, and Xa, Xc are their corresponding input reactances.
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Maximum Power TransferIntroduction
Power transfer formula
where Ra and Rc are the input resistances of the tag antenna and of the chip, respectively, and Xa, Xc are their corresponding input reactances.
Conjugate match between the chip and the antenna
Percentage power transferred to the tag
22 )()(
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caca
ca
XXRR
RRP
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Inductively-Coupled FeedIntroduction
Inductively-coupled feed structure *
* H. W. Son, C.S. Pyo “ Design of RFID tag antennas using an inductively coupled feed ”, Electronics
Letters, vol 41. no. 18, Sep, 2005
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Platform-TolerantIntroduction
Use a patch antenna as the resonating element.
The ground plane isolates the tag antenna from the surface material.
Stable performance regardless of the mounting surface.
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OR-Patch AntennaPatch Antenna
Ground Plane: W1 = 55 mm (0.17 λ) L1 = 109mm(0.33λ)
OR-patch:W2 = 50 mm (0.15 λ) L2 = 83 mm (0.26 λ)
Duroid Substrate: Loss Tangent: 0.0021Dielectric Constant: 3.38Thickness: 1.52 mm
where λ is the freespace wavelength at 915MHzTop view of the OR-patch
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Current Distribution (IE3D)Patch Antenna
At 915MHz,significant current flows around the “ O ” of the patch.
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Return LossPatch Antenna
Measured resonance frequency: 906MHz
Simulated resonance frequency: 915MHz
Percentage error: ~1%
Simulated and Measured S11 of the patch antenna
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Simulated Radiation Pattern (IE3D)Patch Antenna
E-Plane at 915MHz H-Plane at 915MHz
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Simulated Gain (IE3D)Patch Antenna
Simulated gain of the patch antenna
-3
-2
-1
0
1
2
3
4
0.9 0.905 0.91 0.915 0.92 0.925 0.93
Freq (GHz)
Gai
n (
dB
i)
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RFID Tag Antenna
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SpecificationsRFID Tag Antenna
RFID Chip: Philips Electronics
Chip-on-board Impedance at 915MHz: 16-j380Ω
Chip’s Minimum Operating Power at 915MHz: -13dBm
Frequency Band: UHF, 902MHz- 928MHz
Transmitting Antenna Gain (Reader): ~ 6dBi
Transmitting Power (Reader): ~ 30dBm
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Antenna ConfigurationRFID Tag Antenna
Top view of the antenna
Side view of the antennaGround Plane: W1 = 78mm (0.24 λ) L1 = 108mm(0.33 λ)
OR-patch:W2 = 50 mm (0.15 λ) L2 = 82mm (0.25 λ)
Duroid Substrate: Loss Tangent: 0.0021Dielectric Constant: 3.38Thickness: 1.52mm
where λ is the freespace wavelength at 915MHz
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Antenna ConfigurationRFID Tag Antenna
The C-loop is directly connected to the OR-patch
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Range MeasurementRFID Tag Antenna
The read range was measured inside an EMC chamber
Reader antenna was moved inside the EMC chamber
Measure the maximum readable distance that the backscatter signal can be detected.
RFID Tag range measurement using EMC chamber
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Platform-Tolerant Test
RFID Tag Antenna
Following surfaces were used in the test:
Aluminium plate(200 x 200 x 3 mm)
Acrylic resin plate (200 x 200 x 3 mm)
Wood (200 x 200 x 3 mm)
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Simulated Radiation Pattern (IE3D)RFID Tag Antenna
E-Plane at 915MHz H-Plane at 915MHz
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Measured Read RangeRFID Tag Antenna
Read range of the tag antenna mounted on different surfaces
Measured from 902MHz to 928MHz, with a step frequency of 1MHz.
Minimum: 87 cm.
Maximum: 448 cm.
Basically independent of mouting surfaces
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Current DistributionRFID Tag Antenna
902MHz
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Current DistributionRFID Tag Antenna
915MHz
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Current DistributionRFID Tag Antenna
928MHz
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Simulated Power TransferRFID Tag Antenna
Percentage power transfer to the tag
More than 65% across the band.
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ConclusionConclusion
An OR-patch antenna has been investigated.
A platform-tolerant RFID Tag antenna has been designed with the OR-patch.
The feeding loop is connected to the OR-patch directly.
Tests have been carried out using different materials, e.g., metal, plastic, and wood, with little adverse effect on its performance.
The minimum and maximum read ranges are 87cm and 448cm, respectively, across the 902-928 MHz band.
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Thank You!