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Overview

RFID (Radio-frequency identification)

  • Electromagnetic fields to automatically identify and track tags attached to objects
  • These tags contain electronically stored information, and they can be read from a distance without needing line-of-sight.

Tag

  • Contains a microchip (for data) and an antenna (for communication).
    • Passive - no battery, powered by reader signal
    • Active - uses internal battery for longer range/more data
    • Semi-passive - battery-powered, but only responds when activated
Type Frequency (US) Frequency (EU) Units Usage Range Pros Cons
Low (LF) 125–134.2 kHz Same kHz (10³ Hz) Animal tagging, keycards Up to ~10 cm Works well near water/metal, low interference Short range, slow data rate
High (HF) 13.56 MHz Same MHz (10⁶ Hz) NFC, smart cards, library systems Up to ~1 meter Global standard, moderate speed and range Some sensitivity to metal and water
Ultra High (UHF) 902–928 MHz 865–868 MHz MHz (10⁶ Hz) Inventory tracking, supply chain, toll booths Up to ~12 meters Long range, fast data rate, supports many tags at once More affected by metal/liquids, regulated differently

Also, microwave frequecies @ 2.45 GHz but ignoring atm

RFID Tag Data Storage

Low Frequendcy tags, LF

  • chip: EM4100
    • UID (4 bytes)
      • written by manufacturer (unchangeable)
  • chip: T5577
    • changable UID
    • can upload custom rfid response

High Frequency tags, HF

  • Mifare classic
    • UID (4 bytes)
      • written by manufacturer (unchangeable)
    • 16 bytes (1 block) * 4 blocks * 16 sectors = 1024 bytes (writeable)

Some readers can read only a single HF or LF standard.

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