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Radio Frequency Identification (RFID)
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Motivation
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  • The Problem:
    • Identify "tagged"/"labeled" objects
  • The RFID Solution:
    • Use a "tag" that uses radio waves to communicate an identification number to a receiver
Components
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  • Tag/Label:
    • A simple microprocessor
    • A radio transmitter
    • An optional (see below) radio receiver
    • An optional (see below) power source (e.g., battery)
    • An antenna
  • Reader:
    • A microprocessor
    • An optional (see below) radio transmitter
    • A radio receiver
    • An antenna
Classification
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  • Passive Reader, Active Tag:
    • The reader only has a receiver
    • The tag only has a transmitter
    • The tag is "always" transmitting its ID
    • The reader receives and processes the ID
  • Active Reader, Passive Tag:
    • The reader transmits interrogation signals
    • The tag uses the energy transmitted (not an on-board power source) by the reader to transmit its ID
    • The reader receives and processes the ID
  • Active Reader, Active Tag:
    • The reader transmits interrogation signals
    • The interrogation signal informs the tag to transmit
    • The tag uses an on-board power source to transmit its ID
    • The reader receives and processes the ID
Identification Information
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  • Read-Only Tags:
    • The ID is assigned at the factory
  • Read-Write/Field Programmable Tags:
    • ID information can be written (once or many times) in the field
Common Frequencies
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  • 120kHz - 150kHz (Unregulated):
    • Animal "chips"
  • 13.56 MHz (Worldwide ISM):
    • Industrial, Scientific, and Medical
    • Access Control
    • Contactless Smart Cards
  • 433 MHz:
    • Defense
  • 865MHz-868MHz (Europe); 902MHz-928MHz (US):
    • Electronic toll collection
    • Railroad Applications
Options for Passive Tags
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  • Modulation:
    • The tag changes the electrical load which can be detected by the reader
  • Backscatter:
    • The tag reflects the signal back to the reader
There's Always More to Learn
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