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  1. 1. 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
  2. 4. Basic Types of RFID Systems Railroad car monitoring Toll collection systems Long read range High reading speed Line of sight required (Microwave) Expensive High UHF: 850-950MHz Microwave: 2.4 – 5.8 GHz Access Control Smart Cards Short to medium read range Potentially inexpensive Medium reading range Medium 10-15 MHz Access control Animal/Human identification Inventory Control Short to medium read range, inexpensive, low reading speed Low 100-500 kHz Typical Applications Characteristics Frequency Band
  3. 5. Agenda <ul><li>13.56MHz RFID Systems (HF) </li></ul><ul><ul><li>Operating principles are similar to LF </li></ul></ul><ul><li>400-1000MHz RFID Systems (UHF) </li></ul><ul><li>2.4GHz RFID Systems (Microwave) </li></ul>
  4. 6. Why study operating principles? <ul><li>Selecting an RFID system that is most appropriate for your business </li></ul>
  5. 7. Why study operating principles? <ul><li>Business process/RFID system alignment </li></ul><ul><li>According to Michel Porter’s (2001) poor understanding of capabilities offered by e-commerce is what caused, in part, the dot-com crash in 2000 </li></ul>
  6. 9. How to select an appropriate RFID System? <ul><li>For each application, there is an appropriate RFID system in terms of: </li></ul><ul><ul><li>Operating principles </li></ul></ul><ul><ul><ul><li>Frequency </li></ul></ul></ul><ul><ul><ul><li>Range </li></ul></ul></ul><ul><ul><ul><li>Coupling </li></ul></ul></ul><ul><ul><ul><li>etc. </li></ul></ul></ul><ul><ul><li>Functionality </li></ul></ul><ul><ul><ul><li>Read-only </li></ul></ul></ul><ul><ul><ul><li>Read-write </li></ul></ul></ul><ul><ul><ul><li>Motion-detection </li></ul></ul></ul><ul><ul><ul><li>Etc. </li></ul></ul></ul><ul><ul><li>Physical form: </li></ul></ul><ul><ul><ul><li>Stationary readers </li></ul></ul></ul><ul><ul><ul><li>Handheld Readers </li></ul></ul></ul><ul><ul><ul><li>Etc. </li></ul></ul></ul><ul><ul><li>Cost </li></ul></ul>
  7. 10. 13.56MHz RFID Systems Library RFID System from Tagsys Tag Circulation Desk Station Programming Station Inventory Reader Security Gate
  8. 11. 13.56MHz – Operating Principles <ul><li>Mostly passive – no battery </li></ul><ul><ul><li>Low cost </li></ul></ul><ul><ul><li>Longer life-time </li></ul></ul><ul><li>Inductive coupling is used for data transmission </li></ul>
  9. 12. 13.56MHz – Operating Principles Inductive coupling <ul><li>An antenna of the reader generates a magnetic field </li></ul><ul><li>The field induces voltage in the coil of the tag and supplies the tag with energy (Faraday’s Law) </li></ul>
  10. 13. 13.56MHz – Operating Principles Inductive coupling Faraday’s Law <ul><li>Any change in the magnetic environment of a coil of wire will cause a voltage to be &quot;induced&quot; in the coil </li></ul><ul><li>No matter how the change is produced, the voltage will be generated: </li></ul><ul><ul><li>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. </li></ul></ul><ul><li>Implications? </li></ul><ul><ul><li>Interference from “magnets” </li></ul></ul>Source: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html
  11. 14. 13.56MHz – Operating Principles Inductive coupling <ul><li>Data transmission from the reader to the tag is done by changing one parameter of the transmitting field (amplitude, frequency or phase) </li></ul>
  12. 15. 13.56MHz – Operating Principles Inductive coupling <ul><li>Information transmission from the tag to the reader is done by changing amplitude or phase </li></ul>data
  13. 16. 13.56MHz – Operating Principles Inductive coupling Source: AIM Global, 2000
  14. 17. 13.56MHz – Operating Principles <ul><li>13.56MHz are proximity systems </li></ul><ul><li>Operating distance is usually equal the diameter of the reader antenna </li></ul><ul><li>For distances longer than this value, the field strength decreases exponentially (1/d^3) </li></ul><ul><li>The required transmission power increases with the sixth exponent of the distance (d^6) </li></ul>
  15. 18. Distance Field Strength
  16. 19. 13.56MHz – Operating Principles <ul><li>RF field at 13.56MHz is not absorbed by water or human tissue </li></ul><ul><li>Sensitive to metal parts in the operating zone (this applies to all RFID systems) </li></ul><ul><li>As the magnetic field has vector characteristics, tag orientation influences performance of the system (distance) </li></ul><ul><ul><li>Rotating fields </li></ul></ul><ul><li>Since inductive RFID systems are operated in the near field, interference from adjacent systems is lower compared to other systems </li></ul>
  17. 20. 13.56MHz – Operating Principles Tags <ul><li>Tags are available in different shapes and have different functionality </li></ul><ul><li>A few turns (<10) of antenna are sufficient to produce a passive tag  low cost </li></ul>
  18. 21. 13.56MHz – Operating Principles Shape of Tags <ul><li>ISO Cards (ISO 14443, ISO 15693) </li></ul><ul><li>Durable industrial tags </li></ul><ul><li>Thin and flexible smart labels </li></ul>
  19. 22. 13.56MHz – Operating Principles Tag Functionality <ul><li>Memory size (from 64 bit - ID tags to several Kbytes) </li></ul><ul><li>Memory types: ROM, WORM/OTP, R/RW </li></ul><ul><li>Security mechanisms can be implemented </li></ul><ul><li>Multi-tag capability – several tags can be read at once </li></ul>
  20. 23. 13.56MHz – Operating Principles Readers <ul><li>“Proximity” (<1m) </li></ul><ul><ul><li>Handheld devices, printers, terminals </li></ul></ul><ul><ul><li>Small size, low cost </li></ul></ul><ul><li>“Vicinity” (<1.5m) </li></ul><ul><ul><li>More complex </li></ul></ul><ul><ul><li>Higher power consumption </li></ul></ul><ul><li>“Medium range” (<4m) </li></ul>
  21. 24. 13.56MHz – Operating Principles Physical Form of Readers <ul><li>Mobile </li></ul><ul><li>Stationary </li></ul>
  22. 25. 13.56MHz – Operating Principles Physical Form of Readers <ul><li>Readers can have several antennas to allow for: </li></ul><ul><ul><li>Greater operating range </li></ul></ul><ul><ul><li>Greater volume/area coverage </li></ul></ul><ul><ul><li>Random tag orientation </li></ul></ul>
  23. 26. 13.56MHz – Operating Principles Conveyor Performance <ul><li>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 </li></ul>
  24. 27. 13.56MHz – Operating Principles Overall Performance <ul><li>Application fit is the key </li></ul><ul><ul><li>Memory size, security level </li></ul></ul><ul><li>Smaller operating distances allow faster data transmission, longer operating distances impose lower transmission speed </li></ul><ul><li>Greater resistance to noise </li></ul><ul><ul><li>Outside of the ISM band </li></ul></ul>
  25. 28. 400-1000 MHz UHF RFID-Systems (UHF)
  26. 29. 400-1000 MHz UHF RFID-Systems Operating Principles <ul><li>Electromagnetic wave propagation is used for data transmission (and powering transponders in the case of passive tags) </li></ul><ul><li>The reader transmits an electromagnetic (EM) wave which propagates outward </li></ul><ul><li>The amount of energy available is decreasing (1/d^2) as the distance from the reader increases </li></ul>
  27. 30. 400-1000 MHz UHF RFID-Systems Operating Principles
  28. 31. <ul><li>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 </li></ul>400-1000 MHz UHF RFID-Systems Operating Principles
  29. 32. 400-1000 MHz UHF RFID-Systems Operating Principles <ul><li>Operating range is dependent on the radiant power of the reader, the operating frequency, and the size of a tag antenna </li></ul>
  30. 33. 400-1000 MHz UHF RFID-Systems Wave Properties <ul><li>EM waves are related to light and behave in a similar manner </li></ul><ul><li>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 </li></ul><ul><li>UHF waves have shorter waves and, thus, are more effected when passing objects </li></ul>
  31. 34. 400-1000 MHz UHF RFID-Systems Wave Properties - Reflection <ul><li>EM waves can be reflected off any conductive or partially conductive surface, such as metal, water, concrete, etc. </li></ul><ul><li>Reflection can be helpful by causing the waves to be redirected around objects </li></ul><ul><li>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 </li></ul><ul><li>Multiple antennas can solve the problem </li></ul>
  32. 35. 400-1000 MHz UHF RFID-Systems Wave Properties - Reflection
  33. 36. 400-1000 MHz UHF RFID-Systems Wave Properties - Refraction <ul><li>Refraction – the change of direction of a wave due to them entering a new medium (Wikipedia) </li></ul>
  34. 37. 400-1000 MHz UHF RFID-Systems Wave Properties - Refraction
  35. 38. 400-1000 MHz UHF RFID-Systems Wave Properties - Diffraction <ul><li>Diffraction - the spreading out of waves as they pass a sharp corner </li></ul>
  36. 39. 400-1000 MHz UHF RFID-Systems Penetration into Liquids <ul><li>EM waves penetrate into different liquids, depending on the electrical conductivity of the liquid </li></ul><ul><li>Water has high conductivity  will reflect and absorb the signal </li></ul><ul><li>Oil and petroleum liquids have low conductivity  will allow EM to pass </li></ul>
  37. 40. 400-1000 MHz UHF RFID Range <ul><li>Read range depends on: </li></ul><ul><ul><li>Transmitter (reader) power </li></ul></ul><ul><ul><li>Energy requirements of the tags (for passive tags) </li></ul></ul><ul><ul><li>Absorption factor of materials to which the tag is attached </li></ul></ul><ul><ul><li>Tag size </li></ul></ul><ul><ul><ul><li>The smaller the tag, the smaller the energy capture area, the shorter the read range </li></ul></ul></ul>
  38. 41. 400-1000 MHz UHF RFID Interference <ul><li>Electrical noise from motors, florescent lights, etc is minimal at UHF </li></ul><ul><li>Noise from other RFID systems, mobile phones, etc. </li></ul><ul><li>Frequency Hoping Spread Spectrum (FHSS) can reduce interference </li></ul>
  39. 42. 400-1000 MHz UHF RFID Read Direction <ul><li>UHF allows for directional antennas </li></ul><ul><li>This allows to direct the signal to particular groups of tags </li></ul>
  40. 43. <ul><li>Orientation of the tag antenna with respect to the reader’s antenna will impact range (not important for some systems) </li></ul>Tag Orientation
  41. 44. 2450 MHz RFID Systems
  42. 45. 2450 MHz RFID Systems <ul><li>Microwave RFID systems have been in wide-spread use for over 10 years in transportation applications </li></ul><ul><ul><li>Rail car tracking </li></ul></ul><ul><ul><li>Toll collection </li></ul></ul><ul><ul><li>Vehicle access control </li></ul></ul>
  43. 46. 2450 MHz RFID Systems Operating Principles <ul><li>Energy and data transmission using propagating radio signals </li></ul><ul><ul><li>Same as in long-range radio communications </li></ul></ul><ul><li>An antenna of the reader generates a propagating radio wave, which is reflected by the antenna of the tag </li></ul><ul><li>A passive tag converts the signal into voltage supply </li></ul><ul><li>Data transmission from the reader to the tag is done by changing amplitude, frequency, or phase of the transmitting field </li></ul>
  44. 47. 2450 MHz RFID Systems Operating Principles <ul><li>The return transmission from the tag is accomplished by changing the load of the amplitude and/or phase of the signal  modulated backscatter </li></ul><ul><li>Alternatively, a signal of different frequency can be generated, modulated, and transmitted to the reader – “Active RF transmitter tags” </li></ul>
  45. 48. 2450 MHz RFID Systems Operating Principles <ul><li>Microwave systems operate in the “far field”  long range systems </li></ul><ul><li>Microwave signals are attenuated and reflected by materials containing water or human tissue and are reflected by metallic objects </li></ul><ul><ul><li>It is possible to design tags that work on metallic objects </li></ul></ul><ul><li>Line of sight is not required for operations </li></ul>
  46. 49. 2450 MHz RFID Systems Operating Principles <ul><li>UHF and microwave signals easily penetrate wood, paper, cardboard, clothing, paint, dirt, and similar materials </li></ul><ul><li>Because of short wave length and reflective properties of metal, high reading readability can be achieved in meatal-intensive environments </li></ul><ul><li>Sensitive to orientation </li></ul><ul><ul><li>Rotating antennas can solve the problem </li></ul></ul>
  47. 50. 2450 MHz RFID Systems Operating Principles <ul><li>UHF and Microwave systems are allocated many MHz of spectrum  independent operation of different systems, less interference </li></ul><ul><li>Microwave systems have a proven record of reliability </li></ul>
  48. 51. 2450 MHz RFID Systems Physical Form of Tags <ul><li>Tags come in various forms </li></ul><ul><li>Tags are smaller than their LF and HF counterparts </li></ul><ul><li>3 major types of tags </li></ul><ul><ul><li>EZ pass type </li></ul></ul><ul><ul><li>Tags for logistical purposes </li></ul></ul><ul><ul><li>Thin and flexible smart labels </li></ul></ul>
  49. 52. 2450 MHz RFID Systems Tags <ul><li>From 64 bits to several Kbytes </li></ul><ul><li>ROM, OTP, R/RW </li></ul><ul><li>All required security levels can be realized </li></ul><ul><li>Multiple tags can be read in the same zone </li></ul>
  50. 53. 2450 MHz RFID Systems Readers <ul><li>“Proximity” </li></ul><ul><li>“Vicinity” </li></ul><ul><li>Handheld </li></ul><ul><li>Stationary </li></ul>
  51. 54. 2450 MHz RFID Systems Performance <ul><li>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 </li></ul><ul><li>Object penetration and no line-of-sight readability can be better for LF systems </li></ul>
  52. 55. Conclusion <ul><li>Chose the systems which is most appropriate for your application </li></ul>

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