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RFID PRINCIPLES AND APPLICATIONS

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Title: RFID PRINCIPLES AND APPLICATIONS


1
  • 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
2
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

4
Tag reading
The black spot
Normally a very weak reply is obtained
Some application illustrations will be given
shortly
5
Traffic Monitoring
6
Waste Collection
7
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

8
The supply chain
Global Supply Chain
9
  • PART 2
  • THE EMERGING EPC TECHNOLOGY

10
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

11
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

12
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

13
  • PART 3
  • THE KEY CONCEPTS

14
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

15
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

16
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

18
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

19
Material state vectors
20
Laws in differential form
Vortex
Source
21
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
22
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

23
Boundary Condition electric field
24
Boundary Condition magnetic field
25
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

26
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
27
Fields of a Magnetic Dipole(oh dear)
28
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

29
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

30
  • PART 5
  • RFID SYSTEMS

31
Issues in RFID Design
  • Active or passive
  • Operating frequency
  • Electric or magnetic fields
  • Material or microelectronic
  • Focus on passive systems
  • Active for the future?

32
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

33
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

34
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

35
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

36
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

37
Planar printed coil
38
Ferrite cored solenoid
39
Electric field bow tie
40
Electric field box structure
41
Electromagnetic field antenna
  • Dimensions are no longer a small fraction of a
    wave length
  • Operating principles are less clear

42
  • PART 6
  • COUPLING CALCULATIONS

43
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

44
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.

45
Far field coupling theory
46
Near field coupling theory
47
Measures of exciting field
In the far field
48
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

49
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.
50
  • PART 7
  • RFID PROTOCOLS

51
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.

52
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

53
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

54
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

55
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

56
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

57
Tree scanning concepts
58
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

59
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

60
  • PART 6
  • CURRENT DEVELOPMENTS

61
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

62
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

63
The Auto-ID Laboratories
In March 2005 the seventh laboratory was
established at ICU in Korea
64
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

65
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

66
EPCglobal network roles and interfaces
67
  • PART 7
  • CONCLUSIONS

68
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

69
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

70
What to take away 3
  • EPCglobal networking concepts
  • Standardised EPC
  • Standardised readers, tags and protocols
  • Standardised communication between roles

71
  • Thank you
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