RFID PRINCIPLES AND APPLICATIONS

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• RFID PRINCIPLES AND APPLICATIONS

Peter H. Cole Professor of RFID Systems at the
University of Adelaide and Director of the
Auto-ID Laboratory _at_ Adelaide
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Outline

• RFID in the supply chain
• The emerging EPC technology
• The key concepts
• Physics of RFID
• RFID systems
• Coupling calculations
• RFID protocols
• The work of Auto-ID Labs
• Conclusions

3

• PART 1
• RFID IN THE SUPPLY CHAIN

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Tag reading
The black spot
Normally a very weak reply is obtained
Some application illustrations will be given
shortly
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Traffic Monitoring
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Waste Collection
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Example applications

• What can you do with this technology ?
• Supply chain benefits
• Reduce out of stocks, reduce inventory, speed up
  delivery, check freshness, track and trace,
  produce to demand, identify sources of diversion,
  identify counterfeiting, theft prediction, faster
  recalls
• Consumer benefits
• Direct order from home, smart appliances, (e.g.
  microwave, washing machine, refrigerator), smart
  healthcare, assisted living
• New and less expected benefits
• Customized products, smart recycling,
  checkout-less stores

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The supply chain
Global Supply Chain
9

• PART 2
• THE EMERGING EPC TECHNOLOGY

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The Auto-ID Center

• Global, industry funded research program
• Massachusetts Institute of Technology (1999)
• Cambridge University (2000)
• University of Adelaide (2001-2002)
• Japan, China, Switzerland (2003)
• Mission
• Create the internet of things
• Research for the benefit of mankind

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About the Center

• End User Sponsors Include
• Procter Gamble, Gillette, Uniform Codes Council
  (UCC), CHEP International, EAN International,
  International Paper, Philip Morris Group, Johnson
  Johnson, Wal-Mart, Yuen Foong Yu, United States
  Postal Service, Westvaco, Unilever,
  Kimberly-Clark, Tesco, Coca-Cola, Knight Ranger,
  Dai Nippon Printing, Department of Defense,
  United Parcel Service
• Vendor Sponsors Include
• NCR, Savi Technologies, Sun Microsystems, Flint
  Ink, Markem, Invensys, Sensormatic, Cashs,
  Rafsec, Flexchip, Alien Technology, Philips
  Semiconductor, SAP, Checkpoint, ThingMagic,
  Accenture, AC Nielson, Avery Denison, Ember
  Corporation, PWC, Accenture
• Trade Bodies
• AIM Global, GCI, GMA, FMI, NACS, NACDS, AIM,
  POPAI, IMRA, ARTS, UTSA

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The Auto-ID Center Vision

• The internet of things
• Physical objects connected via the internet
• Simple identifying labels on objects
• Unlimited associated data in a data base
• Connections via an intranet or the internet
• Freely available world wide standards
• High performance protocols and software
• A scalable system not choked by expansion

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• PART 3
• THE KEY CONCEPTS

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Key concepts then

• The Electronic Product Code (EPC)
• Tags bearing it and readers reading it
• The Object Name Service (ONS)
• The Physical Mark-up Language (PML)
• Smart scalable networking for the physical world
• The savant, an event manager and router

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Key concepts now

• Electronic product code
• Formats for various applications
• ID system
• Tags and readers
• EPC middleware
• Replaces the savant
• ALE engine and interfaces
• Performs filtering a data routing for clients

• Discovery services
• ONS discovery service
• Discovery services for events
• EPC information services
• Enables users to securely exchange information
  with trading partners

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Use of electromagnetic fields

• Coupling is via electromagnetic fields
• There is little margin for poor performance
• We must understand their properties

17

• PART 4
• THE PHYSICS OF RFID

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The field vectors

• A full theory of electrodynamics, including
  the effects of dielectric and magnetic materials,
  must be based on the four field vectors
• Electric field vector E
• Magnetic field vector H
• Electric flux density vector D
• Magnetic flux density vector B

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Material state vectors
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Laws in differential form
Vortex
Source
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Electromagnetic propagation
Electric current creates a vortex of magnetic
field
Magnetic field creates a vortex of electric field
Electric field creates a vortex of magnetic field
Propagation
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Electromagnetic waves

• They propagate with the velocity of light
• (Light is an electromagnetic wave)
• Velocity c is 300,000,000 m/s
• Wavelength - frequency relation is c fl
• But not all electromagnetic fields are
  propagating waves some are just local energy
  storage fields

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Boundary Condition electric field
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Boundary Condition magnetic field
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The basic laws how they work

• Gausss law
• Electric flux deposits charge
• Electric field cannot just go past a conductor,
  it must turn and meet it at right angles
• Faradays law
• Oscillating magnetic flux induces voltage in a
  loop that it links

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Near and far field distributions
Electric field launched by an electric dipole
There is also a magnetic field not shown
Note the differences between near and far fields
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Fields of a Magnetic Dipole(oh dear)
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Near and far fields

• The far field is an energy propagating field
• Appropriate measure of strength is 0.5 h H2
  (power flowing per unit area)
• The near field is an energy storage field
• Appropriate measure of strength is reactive power
  per unit volume 0.5 w m0H2
• Near field - far field boundary is l/2p
• Examples 100 kHz 500m 10 MHz 5m 1000 MHz 50mm

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The radian sphere

• At br 1, r l/2p, and
• The phase factor e-jbr is one radian
• Inside this sphere the near field predominates
• Outside this sphere the far field predominates

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• PART 5
• RFID SYSTEMS

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Issues in RFID Design

• Active or passive
• Operating frequency
• Electric or magnetic fields
• Material or microelectronic
• Focus on passive systems
• Active for the future?

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The usual way backscatter

• The most popular technology
• Tag contains a microcircuit and an antenna
• Tag is powered by the interrogation beam
• Frequency of that beam is chosen for good
  propagation
• Tag contains an internal oscillator
• Frequency of that oscillator is chosen for low
  power consumption
• Reply is offset from the interrogation frequency
  by a small amount

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Microelectronic Backscatter

• Concept can be applied from 10 MHz to 10,000 MHz
• Low propagation loss points to coupling using the
  far field
• Low power consumption requires a low frequency
  microcircuit
• Reply is by modulation of the interrogation
  frequency

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Relevant Issues

• Range is determined largely by the ability to
  obtain sufficient rectified voltage for the label
  rectifier system
• High quality factor resonance becomes important
  in small tags
• Reply is at sidebands of the interrogation
  frequency

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Interesting features

• Near and far fields
• Energy storage in the near field
• Energy propagation in the far field
• Radian sphere (rl/2p) is the boundary
• Directivity in the far field of 1.5
• No far field radiation in the polar direction
• Plenty of near field on the polar axis

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Label antennas

• Magnetic field free space
• Magnetic field against metal
• Electric field free space
• Electric field against metal
• Electromagnetic field
• Very small antennas respond to either the
  electric field or the magnetic field
• Somewhat larger antennas respond to both

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Planar printed coil
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Ferrite cored solenoid
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Electric field bow tie
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Electric field box structure
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Electromagnetic field antenna

• Dimensions are no longer a small fraction of a
  wave length
• Operating principles are less clear

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• PART 6
• COUPLING CALCULATIONS

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Field creation structures

• Near magnetic field
• Made by current carrying loops
• Near electric field
• Made by charged electrodes
• Far electromagnetic field
• Made by propagation from an originally near field

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Near and far field coupling theories

• Common feature a label driving field is created,
  how much signal can be extracted?
• In the near field of the interrogator, the
  driving field is mostly energy storage, and the
  amount radiated does not affect the coupling, but
  does affect the EMC regulator.
• Various techniques to create energy storage
  without radiating are then applicable.
• Some theorems on optimum antenna size are of
  interest.
• In the far field of the interrogator, the
  relation between what is coupled to and what is
  regulated is more direct, and such techniques are
  not applicable.

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Far field coupling theory
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Near field coupling theory
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Measures of exciting field
In the far field
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Significant conclusions

• Coupling volumes for well shaped planar electric
  and magnetic field labels are size dependent and
  similar
• Radiation quality factors for both types of label
  formed within a square of side L are size
  dependent and similar
• These are calculated results for sensibly shaped
  antennas

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Optimum operating frequency
The optimum frequency for operation of an RFID
system in the far field is the lowest frequency
for which a reasonable match to the radiation
resistance of the label antenna can be achieved,
at the allowed size of label, without the label
or matching element losses intruding.
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• PART 7
• RFID PROTOCOLS

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What is a protocol?

• Signalling waveforms
• Command set
• Operating procedure
• A back end interface
• whereby the identities of a population of tags
  in the field of a reader may be determined, and
  the population otherwise managed.

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Constraints on protocols

• Electromagnetic compatibility regulations
• Differ with frequency range and jurisdiction
• Some convergence is occurring
• Reader to reader interference
• Readers confusing tags
• Readers blocking other reader receivers
• Simplicity (as reflected in chip size)
• Maybe that influences reliability as well

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Auto-ID Center protocols

• The Auto-ID Center defined
• The Class 1 UHF protocol
• The Class 1 HF protocol
• The Class 0 UHF protocol
• EPCglobal has defined in addition
• Generation 2 UHF protocol

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Why are they different?

• Different field properties at HF and UHF
• Near and far field different field confinement
• Different field penetration in materials
• Different silicon circuit possibilities and costs
• Different electromagnetic regulations
• Read only memory technologies enable
  miniaturisation
• A high performance UHF system was available and
  was modified by the Center to manage privacy
  concerns

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Protocols the major divide

• Tree walking
• More forward link signalling
• Prolonged periods of interrupted signalling
• Partial information of tag population remains
  relevant
• Adaptive round (terminating aloha)
• Less forward link signalling
• Long periods of un-modulated reader carrier
• Reader signalling is less
• No information from one response about others

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Characteristics similarities

• Both can select subsets of tags for participation
• Overt selection may reveal what is selected
• Forms of less overt selection are possible
• Tag sleeping has a role in both

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Tree scanning concepts
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Concept of the adaptive round

• Labels reply once per round, in randomly chosen
  slots
• A group of n slots forms a round
• The number of slots in a round varies as needed
• Tags giving already collected replies moved to
  slot F

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The C1G2 protocol

• Labels have an adjustable probability of replying
  on each query or repeated query
• Probability is adjusted to about a third
• Empty slots, singly occupied slots and multiply
  occupied slots are roughly equi-probable
• A wide range of forward and reverse signalling
  parameters are defined
• Some of them allow for narrow band reply
  signalling separated from the interrogation
  carrier

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• PART 6
• CURRENT DEVELOPMENTS

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Auto-ID Center accomplishment

• By September 2003
• Tag reading protocols
• UHF Class 1
• UHF Class 0
• HF Class 1
• Tags (commercial chips to all protocols
  available)
• Savant
• Data filtering and event management software
  system
• Version 1 distributed, version 2 in development
• Field trial
• Three phases, then nearing completion
• PML
• Two phases of development
• Establishment of research laboratories
• USA, England, Australia, China, Japan, Switzerland

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Transformation to Laboratories and EPCglobal

• Transformed
• 26 October 2003
• Auto-ID Labs
• Performs fundamental research related to EPC
  System
• Builds communities not already using EPC System
• EPC Global
• Manages and develops standards
• Markets EPC System

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The Auto-ID Laboratories
In March 2005 the seventh laboratory was
established at ICU in Korea
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Laboratories research program

• Seven laboratories around the world
• Associate laboratories are contemplated
• 96 research topics (original six labs)
• 36 related to propagation and chip design
• 27 related to networking and software
• 35 related to business applications, privacy and
  security
• Korean lab interested in mobile sensor networks

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EPCglobal network outline

• Discovery services
• ONS discovery service
• Discovery services for events
• EPC information services
• Enables users to securely exchange information
  with trading partners

• Electronic product code
• Formats for various applications
• ID system
• Tags and readers
• EPC middleware
• Replaces the savant
• ALE engine and interfaces
• Performs filtering a data routing for clients

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EPCglobal network roles and interfaces
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• PART 7
• CONCLUSIONS

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What to take away 1

• Simplicity of passive RFID for identity
• The weakness of the label reply
• Ubiquity of objects in supply chain
• Vision of the Auto-ID Center
• Electric and magnetic field concepts
• Source and vortex concepts
• Frequency wave length relation c fl

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What to take away 2

• Near and far field concepts
• Radian sphere size and significance
• Boundary conditions near metal
• Behaviour of simple antennas
• Varieties of fast reading protocol
• Transformation of Center
• Auto-ID Labs research

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What to take away 3

• EPCglobal networking concepts
• Standardised EPC
• Standardised readers, tags and protocols
• Standardised communication between roles

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• Thank you