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• RFID stands for Radio Frequency Identification. By means of radio signals, RFID can realize a contactless and unique identification of persons and products on a short range.

• To do this, RFID utilizes so-called tags: electronic labels in which the unique information is saved digitally. This digital information can be read with a special reader unit.

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Passive RFID tags• Passive RFID is of interest because the tags don’t require batteries

or maintenance.• These tags also have an indefinite operational life and are small

enough to fit into a practical adhesive label.• A passive tag consists of three parts: an antenna, a semi conductor

chip attached to the antenna, and some form of encapsulation. • The tag reader is responsible for powering and communicating with

a tag.

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Active RFID Tags

• Active tags require a power source—they’re either connected to a powered infrastructure or use energy stored in an integrated battery.

• Batteries make the cost, size, and lifetime of active tags impractical for the retail trade.

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• Two fundamentally different RFID design approaches exist for transferring power from the reader to the tag: 1. magnetic induction 2. electromagnetic (EM) wave capture

• These two designs take advantage of the EM properties associated with an RF antenna—

the near field and the far field. • Both can transfer enough power to a remote tag to sustain its

operation.

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Near field RFID

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Far field RFID

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Advantages

• No line of sight required• Long range identification feasible• Multiple tags can be detected (nearly)

simultaneously• Operates in harsh environments• Memory to store data on object• Possibility to integrate sensors

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Application • Keyless entry• Electronic Product Code (EPC)• Proximity cards• Security device– Bookstores

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• Human implant ( human identification )• Animal implant ( animal identification)

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References

• K. Finkelzeller, The RFID Handbook, 2nd ed., John Wiley & Sons, 2003.

• M. Weiser, “The Computer for the 21st Century,” Scientific Am., vol. 265, no. 3, 1991, pp. 94–104.

• R. Want, “Enabling Ubiquitous Sensing with RFID,” Computer, vol. 37, no. 4, 2004, pp. 84–86.