Swept-Frequency Tag Reader

Kai-yuh Hsiao (under Joe Paradiso)


  • Uses dynamic imbalance of inductor bridge to detect response from resonant tags
  • Sweeps through 60kHz - 300kHz frequency band at 30 Hz
  • Detects all magnetic tags resonating within sweep frequencies with each sweep
  • Allows for real-time CHI interaction (faster than multi-chip RFID)
  • Inexpensive reader electronics and simple, easily-crafted tag structure permit quick adaptation to CHI, sensing projects
  • Musical demo written, harmonic and melodic changes reflect tag presence
    • Tag resonance frequency can be made to vary with physical parameters (e.g., force, position, etc.)
    • Voltage output reflects tag orientation and proximity to coil, enabling continuous response
    • Simplicity, safety, and tag structure very well suited to many applications, including toys

updated 1998/10/4 by khsiao@mit.edu