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 f 0 = 897 MHz, β = 0.165

20. Figure 3.19 Return loss for circuit with f 0 = 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 mm 2 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).