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CST User Workshop

Online Design of UHF RFID Antennas Assisted by CST Microwave Studio

Devin Crawford, Sr. Application Engineer Transim Technology Corporation

7/2/2013

7/2/2013 2 Transim Technology Corporation - Confidential Information!

Introduction to Transim

Web 2.0

Overview of UHF RFID Tagging

Implementation of the RFID PCB Antenna Designer

Live Demo

Outline


Key Milestones

Introduction to Transim 1992

Release of Simplis: linearized SPICE for switching systems.

WebSIMTM Patent for online simulation.

Release of Web BenchTM for National Semiconductor.

• Transim purchased by Arrow Electronics. • Continued operation as independent

business unit.

2008

2013

1991

Transim founded by Tom Wilson and Ron Wong

2010

• Reorganization and re-focus on online design. • Divest Simplis Technologies.

Web 1.0

• Online antenna design site for NXP Semiconductor • Online access to full-wave EM Solver (Microwave Studio)

2000

1998

Growth of online design

...emphasis on power.

Web 2.0

Transim

Web Development

Engineering

FAE

FAE

FAE

5

Scalable Engineering Support

Scalable / Broad Market / Long Tail Application Engineering Support

Top tier specialty and design-in support

Design Database

Potential Customers Seeking Help

7/2/2013 Transim Technology Corporation - Confidential Information!

Expertise

Expertise

eFAE

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Transim and NXP

8

Some Customers and Partners

7/2/2013 Transim Technology Corporation - Confidential Information!

http://arrow.transim.com/designweb

Evolution of the Web


Wolrd Wide Web 2.0


World Wide Web ◦ Server/Client interaction over a network enables

transmission of data.

Hypertext Markup Language (HTML) ◦ Standardized syntax for displaying text, pictures and

embedding information in web pages.

Worldwide Web (Web 1.0)

???


Worldwide Web 1.0


Web 2.0 ◦ Users interact with the web page. Information flow is in

both directions.

Worldwide Web (Web 2.0)

101101010

The displayed page reacts to user actions.

Computation burden transferred to server.

Multiple users interact within an application.


Web 2.0

Online interactive schematic capture http://arrow.transim.com/envision


Web 2.0

Online integrated design environment. http://arrow.transim.com/bemicro

• Compile code on the „could.“

• Save/Share/Load

• Syntax highlighting.

• Interface to hardware via USB.

• Web-based UI that interacts with hardware.

Design Challenge for RFID Tag Antennas


RFID


Radio Frequency Identification ◦ Active Reader / Passive Tag

RFID

High performance reader.

Passive tags on individual products. (very low cost)

Connection to local network, manufacturing database, etc.


UHF RFID

◦ Standardization through EPCglobal (Electronic Product Coding).

◦ „Class 1, 2nd Generation“ Active reader passive tag.

Applications: ◦ Inventory and tracking.

◦ Healthcare.

◦ Electronic payment.

◦ Asset management.

◦ Telemetry.

Antenna Design for UHF RFID

Ultra High Frequency Radio Frequency Identification


Tag Antenna Design ◦ Customers who use RFID tags often have little knowledge

about antenna design.

◦ The antenna must be small and cost „nothing“.

◦ The input to the tag IC is capacitive with a small real part.

RFID Tag Design Challenge

Tag IC

Tag IC & Package Antenna


The maximum obtainable read distance is determined by: ◦ Incident power: Reader EIRP.

◦ Tag IC Sensitivity. (Typically given in dBm)

◦ Polarization mismatch. (Reader is usually circular polarized)

◦ Impedance mismatch between tag IC and tag antenna.

◦ Gain of the tag antenna.

Tag Antennas on Printed Circuit Boards

Tag IC

Tag IC & Package

Antenna


Tag antenna is part of the PCB layout.

Transponder radiated power is mandated in terms of

Tag Antennas on Printed Circuit Boards

ERP:

EIRP:

Refererred to a l/2 dipole with 2.15 dBi gain.

Refererred to an isotropic radiator. North America

Europe

For example ◦ United States (FCC) specifies 4 Watt EIRP for the reader.

◦ EU (ETSI) specifies 2 Watt ERP:

The peak radiated power density measured 1 meter from the transmitter may not exceed 4W/(4p)m2 = 0.320 W/m2 at any measurement direction.

1.64 x 2 / (4p) = 0.261 W/m2 in any direction at 1 meter distance.


Power received by the tag IC

Maximum read distance

RFID Read Distance

𝑃tag = 𝑃reader

𝐺reader𝐺tag𝑐2

4𝜋𝑓𝑟 𝟐 1 − 𝛤 2

EIRP IC sensitivity

Impedance mismatch between tag antenna and tag IC

Reader to tag distance.

Gain of the tag antenna.

𝑟 =𝑐

4𝜋𝑓

𝑝𝜂 1 − 𝛤 2 EIRP ∙ 𝐺tag

𝑠

s

p 0.5 to account for polarization mismatch.

η ̴0.8 to account for IC internal loss.


Generalized power wave scattering parameters. ◦ Antenna and IC have complex impedance.

Mismtach Loss

E0

ZA

ZC Vi

+

-

Ii

Antenna

Power waves:

𝑎𝑖 =𝑉𝑖 + 𝑍𝐴𝐼𝑖

2 𝑅𝑒 𝑍𝐴

𝑏𝑖 =𝑉𝑖 − 𝑍𝐴

∗𝐼𝑖

2 𝑅𝑒 𝑍𝐴

IC

Available power:

𝑎𝑖2 =

𝐸02

4𝑅𝑒 𝑍𝐴 ≝ 𝑝𝑖

Power delivered to the IC:

𝑝𝑐 = 𝑝𝑖 𝑎𝑖2 − 𝑏𝑖

2 Γ =

𝑏𝑖

𝑎𝑖=

𝑍𝐶 − 𝑍𝐴∗

𝑍𝐶 + 𝑍𝐴

Reflection coefficient for a complex source and load impedance:

K. Kurokawa, Power Waves and the Scattering Matrix, IEEE Trans. Microw. Theory Tech., Vol 13, N.2 (1965)

RFID PCB Antenna Designer


Online Antenna Design


RFID PCB Antenna Design Flow

Sensitivity and chip impedance.

Geographical region Area available for the antenna

Fast optimization with reduced degrees of freedom.

Select IC

Specify design parameters.

Optimize surrogate model.

Modify additional degrees of freedom.

Validate

Postprocessing and download.

Modify parameters not considered in surrogate model.

Full-wave 3D EM Simulation in Microwave Studio to validate the design.

View and download results. Download models and antenna layout.

Information obtained: Design Step



nxp.transim.com/rfid

Select IC




Specify design parameters. Region

Available area

Outer layer type.





Antenna topology and dimensions provide the starting point for optimization.

Dimensions

Layout preview

Read distance and return loss.




Optimized antenna.

Time required: • Typical < 20 seconds




Available Topologies

„Bend Slot

„Meander Slot

„Loop Dipole




Validate





• Compare approximate results from the surrogate model with the full-wave EM simulation.

• Simulation takes 4-8 minutes. • Run on the „cloud“.





• 3D read distance. • Dynamic visualization with zoom and rotate. • No plugins – HTML5




E-Field H-Field






Download • Microwave Studio Model • DXF layout with IC footprint • PDF summary • Data in Excel format.


Transim leverages the latest web technology to provide interactive, online engineering solutions.

RFID Tag Antenna Design on PCBs ◦ UHF RFID Overview ◦ Parameters affecting read distance. ◦ S-parameters with complex source impedance.

NXP RFID Antenna Designer

◦ Step by step guidance for novice users ◦ Full-wave 3D Simulation with Microwave Studio ◦ Fast and easy custom antenna design for NXP RFID IC‘s.

Summary

online design of uhf rfid antennas assisted by cst ... · transim technology corporation ... the...

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