A Metamaterial-Based Series Connected Rectangular Patch Antenna Array for UHF RFID Readers

Benjamin D. BraatenSayan Roy*

Sanjay NariyalMasud A. Aziz

Bilal IjazMuhammad M. Masud

ECE DepartmentNorth Dakota State University

Fargo, ND, USA.

APPLIED ELECTROMAGNETICS LAB

NORTH DAKOTA STATE UNIVERSITY

1) Introduction and Background

2) The Metamaterial-Based UHF RFID Antenna

3) Measurement and Simulation Results

4) Discussion and Guidelines

5) Conclusion

Topics

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Introduction and BackgroundThe proposed metamaterial-based UHF RFID reader antenna:

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The design consists of the following features:

1) Rectangular patches

2) Inter-digital capacitors

3) Tuning stub

4) Series fed array

Reference: S. Paulotto, P. Baccarelli, F. Frezza and D. R. Jackson, “A microstrip periodic leaky-wave antenna optimized for broadside scanning,” IEEE International Symposium on Antennas and Propagation, June 9-15, 2007, pp. 5789-5792.

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The Manufactured Prototypea = 2.15 mmb = 17.19 mmc = 3.1 mmd = 23.6 mme = 32.0 mmf = 6.2 mmg = 5.6 mmh = 13.0 mmj = 8.87 mmk = 41.4 mmm =55.95 mmn = 5.6 mm

p = 44.59 mmq = 8.8 mmW =136.38 mmH = 83.5 mmFinger spacing = 0.8 mmFinger width = 0.4 mmFinger length = 0.5 mm

Substrate:Thickness: 1.58 mmPermittivity: 4.3 (FR4)

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S-parameters of a Single Array

A resonant frequency of 920 MHz can be observed.

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Series Fed-arrays Under Test

Texas Instruments Passive UHF RFID tag [1]:Read sensitivity: - 13 dBmWrite sensitivity: -9 dBm

[1] Texas Instruments, [online], www.ti.com

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Series Fed-arrays Under Test

Two UHF RFID reader

antennas, mounted on a

Styrofoam block, connected

in series in the anechoic

chamber, formed as a

travelling wave antenna.

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Coverage results

Good coverage up to 22.86 cm.

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Normalized fields at 920 MHz

x-z plane y-z plane

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Simulated Surface Currents at 920 MHz

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Antenna Design

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Design Guidelines1) Simulated S-parameters for a

single metamaterial-based RFID reader antenna for various values of m (stub length).

2) The stub width n was also varied in a similar manner and no change in the resonant frequency was observed.

3) Similarly, the dimensions of the patch were increased and decreased by 15% and very little change in resonant frequency was observed.

1) The S-parameter results in this work show that a compact UHF RFID reader antenna can be developed for near-field UHF RFID applications.

2) The read-range measurements show that spatially broad near-field coverage can be achieved by connecting multiple antenna in series. This coverage can also be observed from the simulated fields.

3) The simulated currents show that this antenna supports current on the radiating patches and the matching stub.

Discussion

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1) A new metamaterial-based UHF RFID reader antenna has been presented.

2) This antenna can be connected in series for broad near-field coverage at 920 MHz.

3) Measurement and simulation results were compared.

4) Initial discussion and guidelines on designing the antenna have been presented.

Conclusion

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Thank you for listening!

Questions?

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