the full system rfid methodology

1 © 2014 ANSYS, Inc. November 12, 2015 ANSYS Confidential

The Full System RFID Methodology


State of the art simulation method that

• utilizes the best in class tools

• incorporates actual RFID transponder,

• tag geometries, and TX/RX circuits

• uses “real world” signalling schemes

• takes into account entire operating environment

• seamlessly combines frequency and time

• domain results

What is a Full System RFID Methodology


Transponder and Tag Modeling

• HFSS

Full 3D Environment Simulation

• HFSS

“Real World” Transponder and Tag Circuitry

• Designer

Realistic transmit/received, backscattered signals

• Designer

Methodology Enablers

• HPC

What are the tools needed


Premier 3D Electromagnetic design tool

Solves

• Any arbitrary 3D structure

Uses • Full Wave Finite Element Method (FEM) • Transient Finite Element Solver • Integral Equation Solver • Physical Optics Solver Applications • Antennas • Waveguides • Filters • Integrated circuit (IC) packages • Connectors • Vias • Transitions • LTCC devices • MMIC devices • Radar equipment • Cell phones • Satellite equipment • Bio-Medical equipment • Wireless components • EMI/EMC • Etc. etc. etc.

HFSS


Seamlessly integrates ANSYS HF tools together for full system simulations

Solves

• Time / frequency circuit and system simulator

Uses

• State Space or convolution

• Time domain spice solver

• Harmonic Balance frequency domain solver

• 2D / 3D Method of Moment solver

Applications

• Time and / or frequency domain circuit analysis

• Time and / or frequency domain system design

• Signal Integrity

• Antenna Arrays

• RF IC simulation

What is Designer


Distributed memory parallel solver technique

Distributes mesh sub-domains to network of processors

Significantly increases simulation capacity

Highly scalable to large numbers of processors

Automatic generation of domains by mesh partitioning

• User friendly

• Load balance

Hybrid iterative & direct solver

• Multi-frontal direct solver for each sub-domain

• Sub-domains exchange information iteratively via Robin’s transmission conditions (RTC)

What is HPC

Distributes mesh sub-domains

to networked processors and memory


Use HFSS to design / optimize Transponder and Tag antennas

Use Designer to design / optimize Transponder and Tag circuitry

Create 3D model of Full RFID System environment

Link all above models together in Designer Schematic

Obtain Full Systems performance data / metrics

What are the steps


Transponder Antenna Specifications

• Operating Frequency of 920 MHz

• 50 ohm input impedance

• Circularly polarized

• Return loss of -15 dB or better

• Gain of 6dB or better

• Cross polarization >15 dB

Transponder Antenna Design in HFSS

Full 3D model of Antenna Radome shown as transparent for clarity

Cross sectional view of Antenna


New Capability for sensitivity, tuning, and optimization

Compute the derivatives of SYZ parameters with respect to project and design variables

Eliminates need to solve multiple variations with small differences and numerical noise

• More efficient and more accurate

Provides real-time tuning of reports to explore effects of small design changes

Improves derivative-based optimization methods

Rapid Antenna Tuning using Adjoint Derivatives Functionality


Final Transponder Antenna Results

Return Loss

3D Far field Pattern

(superimposed on

Antenna Cover)

Far Field pattern

LH and RH

circular polarization

Electric Field on

substrate surface

and Current vectors

on antenna


Tag Antenna Specifications

• Operating Frequency of 920 MHz

• Backscatter link frequency 250 KHz

• Omni-directional antenna pattern

• Antenna impedance matched to 5 – j10 ohms

• Dustproof and waterproof

RFID Tag Antenna Design in HFSS

5 mm thick

Top half of tag cut away


Final RFID Tag Antenna Results

Return Loss

Input Impedance 3D Antenna pattern

2D Antenna pattern


Designer Transmit Circuit


Transmit Circuit Results


Designer can “push” output results to HFSS so that a realistic far field pattern can be created

Antenna Far Field Pattern


RFID Tag Circuit (RF/Analog Frontend)

Power Generation and Management

AM Demodulator

BS Modulator

rectifier (charge pump),

limiter,

DC voltage regulator

envelope detector

simple comparator

Switching capacitor


Charge Pump Circuit

Charge pump optimization


Voltage Limiter/Regulator Circuit


AM Demodulator Circuit


Backscattering Modulator Circuit


Overall Tag Circuit Response (Ideal RF source)

RF Input Backscattering Modulation


Realistic Environment HFSS model

2.5 m

Side View

Top View Front View

Transponder Antenna

Steel rod reinforced concrete columns

Aluminum roller conveyor system

Cardboard shipping container

Metal container inside container

Tag on exterior of container

3D View

1.5 m

2m


Full System Model (Combining all the models)

Transponder Circuitry

Realistic Environment

Tag Circuitry


Full System Field Results

Full System TX Antenna patterns


Full System Field Results

Tag located on front of shipping container

Tag located on top of shipping container

Main lobe points in wrong direction Main lobe points in proper direction


Tag Signals at Transponder receiver input

Full System Tag Results

RF Input Backscattering Modulation


Receiver input spectral response

(Tag backscatter frequency is 250 KHz)

Full System Transponder Results

No tag in interrogation zone Tag in interrogation zone

m3 = fo – fbs

m2 = fo + fbs


Even Larger Environments

24 Tags, 4 Reader Antennas

900 MHz operating frequency

2 Warehouse bays

20 GB of RAM Total

1.8 GB of RAM per node

11 nodes

< 4 Hr Solve Time

18

fe

et

16

fe

et


Using the combination of HFSS and Designer it is easily possible to design, optimize, and predict the performance of an RFID system in its intended environment.

Additionally, multiple arbitrarily located and oriented tags can be included in the model as well.

Larger environments are possible.

Random noise sources can also be included in the full system model.

Final thoughts

the full system rfid methodology

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