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Chapter 3 - UHF RFID Antennas

Chapter 3 - UHF RFID Antennas. Figure 3.1 commercially UHF RFID tags. Figure 3.2 Electric and magnetic fields around a dipole antenna. Figure 3.3 Simple circuit model of dipole antenna near resonance. Figure 3.4 Radiation pattern around a dipole antenna.

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Chapter 3 - UHF RFID Antennas

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  1. Chapter 3 - UHF RFID Antennas

  2. Figure 3.1 commercially UHF RFID tags

  3. Figure 3.2 Electric and magnetic fields around a dipole antenna

  4. Figure 3.3 Simple circuit model of dipole antenna near resonance

  5. Figure 3.4 Radiation pattern around a dipole antenna

  6. Figure 3.5 Relationship between cylindrical and ribbon dipoles

  7. Figure 3.6 Straight vs. meandering dipole

  8. Figure 3.7 commercial tip-loaded dipole tags

  9. Figure 3.8 Spiral-loaded tag

  10. Figure 3.9

  11. Figure 3.10

  12. Figure 3.11 Uda's circuit model of T-match

  13. Figure 3.12 Smith chart view of impedance matching using the T-match

  14. Figure 3.13 Intuitive inductor-based circuit model for the T-match

  15. Figure 3.14 New inductor-based circuit model of the T-match dipole

  16. Figure 3.15 Transformed circuit model of RFID tag

  17. Figure 3.16 Meandering dipole used in the first cut

  18. Figure 3.17 Circuit model of proposed antenna

  19. Figure 3.18 Return loss for circuit with f0 = 897 MHz, β = 0.165

  20. Figure 3.19 Return loss for circuit with f0 = 890 MHz, β = 0.17

  21. Figure 3.20 Circuit predicted impedance looking into antenna

  22. Figure 3.21 Geometry of matching circuit

  23. Figure 3.22 Geometry of the completed antenna

  24. Figure 3.23 Return loss of circuit and simulated antenna

  25. Figure 3.24 Radiation pattern of designed antenna

  26. Figure 3.25 Tag on semi-infinite dielectric

  27. Figure 3.26 Tag operating above a ground plane, shown with image

  28. Figure 3.27 Impedance of a near-resonant dipole above a 300 mm2 ground plane

  29. Figure 3.28 Microstrip antenna fed by a microstrip transmission line

  30. Figure 3.29 Transmission line model of a microstrip antenna

  31. Figure 3.30 Traditional unbalanced way to feed the microstrip antenna top bottom

  32. Figure 3.31 Narrowband microstrip antenna

  33. Figure 3.32 Large, wideband microstrip antenna

  34. Figure 3.33 Impedance of variable length dipole in free space (left) and 3.2 mm separation from an infinite metal ground plane (right)

  35. Figure 3.34 Permissible region

  36. Figure 3.35 A prototype microstrip antenna

  37. Figure 3.36 A combined dipole / microstrip antenna

  38. Figure 3.37 Circuit model of combined dipole / microstrip antenna functioning in air

  39. Figure 3.38 Circuit model of combined dipole / microstrip antenna functioning on metal

  40. Figure 3.39 (a) dipole / microstrip antenna in air

  41. Figure 3.39 (b) dipole / microstrip antenna on metal

  42. Figure 3.40 (a) Power transfer efficiency of combined dipole / microstrip antenna in air

  43. Figure 3.40 (b) Power transfer efficiency of combined dipole / microstrip antenna on metal (b).

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