RFID Systems and Operating Principles

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RFID Systems and Operating Principles

• Vlad Krotov
• DISC 4397 Section 12977
• University of Houston
• Bauer College of Business
• Spring 2005
• Presentation Source AIM Global, 2000

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Basic Types of RFID Systems
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Agenda

• 13.56MHz RFID Systems (HF)
• Operating principles are similar to LF
• 400-1000MHz RFID Systems (UHF)
• 2.4GHz RFID Systems (Microwave)

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Why study operating principles?

• Selecting an RFID system that is most appropriate
  for your business

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Why study operating principles?

• Business process/RFID system alignment
• According to Michel Porters (2001) poor
  understanding of capabilities offered by
  e-commerce is what caused, in part, the dot-com
  crash in 2000

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How to select an appropriate RFID System?

• For each application, there is an appropriate
  RFID system in terms of
• Operating principles
• Frequency
• Range
• Coupling
• etc.
• Functionality
• Read-only
• Read-write
• Motion-detection
• Etc.
• Physical form
• Stationary readers
• Handheld Readers
• Etc.
• Cost

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13.56MHz RFID Systems
Library RFID System from Tagsys
Tag
Circulation Desk Station
Inventory Reader
Programming Station
Security Gate
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13.56MHz Operating Principles

• Mostly passive no battery
• Low cost
• Longer life-time
• Inductive coupling is used for data transmission

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13.56MHz Operating Principles Inductive
coupling

• An antenna of the reader generates a magnetic
  field
• The field induces voltage in the coil of the tag
  and supplies the tag with energy (Faradays Law)

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13.56MHz Operating Principles Inductive
couplingFaradays Law

• Any change in the magnetic environment of a coil
  of wire will cause a voltage to be "induced" in
  the coil
• No matter how the change is produced, the voltage
  will be generated
• The change could be produced by changing the
  magnetic field strength, moving a magnet toward
  or away from the coil, moving the coil into or
  out of the magnetic field, rotating the coil
  relative to the magnet, etc.
• Implications?
• Interference from magnets

Source http//hyperphysics.phy-astr.gsu.edu/hbase
/electric/farlaw.html
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13.56MHz Operating Principles Inductive coupling

• Data transmission from the reader to the tag is
  done by changing one parameter of the
  transmitting field (amplitude, frequency or phase)

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13.56MHz Operating Principles Inductive
coupling

• Information transmission from the tag to the
  reader is done by changing amplitude or phase

data
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13.56MHz Operating Principles Inductive
coupling
Source AIM Global, 2000
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13.56MHz Operating Principles

• 13.56MHz are proximity systems
• Operating distance is usually equal the diameter
  of the reader antenna
• For distances longer than this value, the field
  strength decreases exponentially (1/d3)
• The required transmission power increases with
  the sixth exponent of the distance (d6)

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Field Strength
Distance
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13.56MHz Operating Principles

• RF field at 13.56MHz is not absorbed by water or
  human tissue
• Sensitive to metal parts in the operating zone
  (this applies to all RFID systems)
• As the magnetic field has vector characteristics,
  tag orientation influences performance of the
  system (distance)
• Rotating fields
• Since inductive RFID systems are operated in the
  near field, interference from adjacent systems is
  lower compared to other systems

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13.56MHz Operating Principles Tags

• Tags are available in different shapes and have
  different functionality
• A few turns (lt10) of antenna are sufficient to
  produce a passive tag ? low cost

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13.56MHz Operating Principles Shape of Tags

• ISO Cards (ISO 14443, ISO 15693)
• Durable industrial tags
• Thin and flexible smart labels

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13.56MHz Operating Principles Tag Functionality

• Memory size (from 64 bit - ID tags to several
  Kbytes)
• Memory types ROM, WORM/OTP, R/RW
• Security mechanisms can be implemented
• Multi-tag capability several tags can be read
  at once

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13.56MHz Operating Principles Readers

• Proximity (lt1m)
• Handheld devices, printers, terminals
• Small size, low cost
• Vicinity (lt1.5m)
• More complex
• Higher power consumption
• Medium range (lt4m)

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13.56MHz Operating Principles Physical Form of
Readers

• Mobile
• Stationary

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13.56MHz Operating Principles Physical Form of
Readers

• Readers can have several antennas to allow for
• Greater operating range
• Greater volume/area coverage
• Random tag orientation

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13.56MHz Operating PrinciplesConveyor
Performance

• A reader that reads 10 to 30 tags per second ?
  Successful tagging of items on a conveyor running
  at 3 m/s and spaced 0.10 m

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13.56MHz Operating PrinciplesOverall
Performance

• Application fit is the key
• Memory size, security level
• Smaller operating distances allow faster data
  transmission, longer operating distances impose
  lower transmission speed
• Greater resistance to noise
• Outside of the ISM band

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400-1000 MHz UHF RFID-Systems (UHF)
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400-1000 MHz UHF RFID-SystemsOperating Principles

• Electromagnetic wave propagation is used for data
  transmission (and powering transponders in the
  case of passive tags)
• The reader transmits an electromagnetic (EM) wave
  which propagates outward
• The amount of energy available is decreasing
  (1/d2) as the distance from the reader increases

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400-1000 MHz UHF RFID-SystemsOperating Principles
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400-1000 MHz UHF RFID-SystemsOperating Principles

• The amount of energy collected is a function of
  the aperture of the receiving antenna, which in
  simple terms is related to the wavelength of the
  received signal

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400-1000 MHz UHF RFID-SystemsOperating Principles

• Operating range is dependent on the radiant power
  of the reader, the operating frequency, and the
  size of a tag antenna

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400-1000 MHz UHF RFID-SystemsWave Properties

• EM waves are related to light and behave in a
  similar manner
• EM waves can be reflected off radio conductive
  reflective surfaces, refracted as they pass the
  barrier between dissimilar electric media, or
  detracted around a sharp edge
• UHF waves have shorter waves and, thus, are more
  effected when passing objects

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400-1000 MHz UHF RFID-SystemsWave Properties -
Reflection

• EM waves can be reflected off any conductive or
  partially conductive surface, such as metal,
  water, concrete, etc.
• Reflection can be helpful by causing the waves to
  be redirected around objects
• Reflection can also cause a problem if a direct
  wave meets with a reflected wave with an opposite
  phase ? wave cancellation can occur resulting a
  no-read situation
• Multiple antennas can solve the problem

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400-1000 MHz UHF RFID-SystemsWave Properties -
Reflection
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400-1000 MHz UHF RFID-SystemsWave Properties -
Refraction

• Refraction the change of direction of a wave
  due to them entering a new medium (Wikipedia)

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400-1000 MHz UHF RFID-SystemsWave Properties -
Refraction
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400-1000 MHz UHF RFID-SystemsWave Properties -
Diffraction

• Diffraction - the spreading out of waves as they
  pass a sharp corner

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400-1000 MHz UHF RFID-SystemsPenetration into
Liquids

• EM waves penetrate into different liquids,
  depending on the electrical conductivity of the
  liquid
• Water has high conductivity ? will reflect and
  absorb the signal
• Oil and petroleum liquids have low conductivity
  ? will allow EM to pass

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400-1000 MHz UHF RFIDRange

• Read range depends on
• Transmitter (reader) power
• Energy requirements of the tags (for passive
  tags)
• Absorption factor of materials to which the tag
  is attached
• Tag size
• The smaller the tag, the smaller the energy
  capture area, the shorter the read range

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400-1000 MHz UHF RFIDInterference

• Electrical noise from motors, florescent lights,
  etc is minimal at UHF
• Noise from other RFID systems, mobile phones,
  etc.
• Frequency Hoping Spread Spectrum (FHSS) can
  reduce interference

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400-1000 MHz UHF RFIDRead Direction

• UHF allows for directional antennas
• This allows to direct the signal to particular
  groups of tags

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Tag Orientation

• Orientation of the tag antenna with respect to
  the readers antenna will impact range (not
  important for some systems)

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2450 MHz RFID Systems
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2450 MHz RFID Systems

• Microwave RFID systems have been in wide-spread
  use for over 10 years in transportation
  applications
• Rail car tracking
• Toll collection
• Vehicle access control

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2450 MHz RFID SystemsOperating Principles

• Energy and data transmission using propagating
  radio signals
• Same as in long-range radio communications
• An antenna of the reader generates a propagating
  radio wave, which is reflected by the antenna of
  the tag
• A passive tag converts the signal into voltage
  supply
• Data transmission from the reader to the tag is
  done by changing amplitude, frequency, or phase
  of the transmitting field

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2450 MHz RFID SystemsOperating Principles

• The return transmission from the tag is
  accomplished by changing the load of the
  amplitude and/or phase of the signal ? modulated
  backscatter
• Alternatively, a signal of different frequency
  can be generated, modulated, and transmitted to
  the reader Active RF transmitter tags

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2450 MHz RFID SystemsOperating Principles

• Microwave systems operate in the far field ?
  long range systems
• Microwave signals are attenuated and reflected by
  materials containing water or human tissue and
  are reflected by metallic objects
• It is possible to design tags that work on
  metallic objects
• Line of sight is not required for operations

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2450 MHz RFID SystemsOperating Principles

• UHF and microwave signals easily penetrate wood,
  paper, cardboard, clothing, paint, dirt, and
  similar materials
• Because of short wave length and reflective
  properties of metal, high reading readability can
  be achieved in meatal-intensive environments
• Sensitive to orientation
• Rotating antennas can solve the problem

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2450 MHz RFID SystemsOperating Principles

• UHF and Microwave systems are allocated many MHz
  of spectrum ? independent operation of different
  systems, less interference
• Microwave systems have a proven record of
  reliability

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2450 MHz RFID SystemsPhysical Form of Tags

• Tags come in various forms
• Tags are smaller than their LF and HF
  counterparts
• 3 major types of tags
• EZ pass type
• Tags for logistical purposes
• Thin and flexible smart labels

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2450 MHz RFID SystemsTags

• From 64 bits to several Kbytes
• ROM, OTP, R/RW
• All required security levels can be realized
• Multiple tags can be read in the same zone

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2450 MHz RFID SystemsReaders

• Proximity
• Vicinity
• Handheld
• Stationary

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2450 MHz RFID SystemsPerformance

• Compared to inductive systems, the UHF and
  microwave systems can have longer range, higher
  data rates, smaller antennas, more flexibility in
  form factors and antenna design
• Object penetration and no line-of-sight
  readability can be better for LF systems

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Conclusion

• Chose the systems which is most appropriate for
  your application