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ANALYSIS OF CONSTRAINTS IN SMALL UHF RFID TAG DESIGN

Mun Leng Ng Auto-ID Lab @ Adelaide School of Electrical & Electronic Engineering University of Adelaide Australia mng@eleceng.adelaide.edu.au. ANALYSIS OF CONSTRAINTS IN SMALL UHF RFID TAG DESIGN. Introduction on RFID. What is RFID? RFID basic components:. RFID Tag. Consist of

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ANALYSIS OF CONSTRAINTS IN SMALL UHF RFID TAG DESIGN

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  1. Mun Leng Ng Auto-ID Lab @ Adelaide School of Electrical & Electronic Engineering University of Adelaide Australia mng@eleceng.adelaide.edu.au ANALYSIS OF CONSTRAINTS IN SMALL UHF RFID TAG DESIGN

  2. Introduction on RFID • What is RFID? • RFID basic components:

  3. RFID Tag • Consist of • Basic requirement:- Compact- Reliable- Inexpensive

  4. The Constraints • Bandwidth limitation on impedance matching • Tag antenna size constraint towards impedance matching

  5. Bandwidth Limitation

  6. Bode-Fano Limit

  7. Bode-Fano Limit (cont)

  8. Application of Bode-Fano Limit on RFID • Allocated bandwidths for RFID: • Others:China: 917 – 922 MHz (Temporary license can be applied)Australia: 918 – 926 MHz

  9. Application of Bode-Fano Limit on RFID • 3 different cases considered:

  10. Application of Bode-Fano Limit on RFID • Assume R = 1 k, C = 1 pF • R = 10 k, C = 1 pF (for less power consuming tag chip in practice)

  11. Tag Antenna Size Constraint

  12. A Simple Loop Antenna • Single-turn circular loop antenna:

  13. Overall Circuit Qant = (2f L)/Rr Qchip = f0/f

  14. Results • When Qant = Qchip: - D = 9.65 cm - Impedance of antenna approximately 5 times impedance of chip • If R = 10 k, C = 1 pF: - D = 4.48 cm - Smaller difference between tag antenna and chip impedances

  15. A Simple RFID Tag Copper foil tuning strap for impedance matching Butterfly antenna (a modified bow-tie)

  16. A Simple RFID Tag (cont) • Simplified equivalent circuit:

  17. Another Simple RFID Tag • Consists of a circular loop antenna with a very simple matching network FRONT REAR

  18. Conclusion

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