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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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Figure 3.2 Electric and magnetic fields around a dipole antenna
Figure 3.3 Simple circuit model of dipole antenna near resonance
Figure 3.5 Relationship between cylindrical and ribbon dipoles
Figure 3.12 Smith chart view of impedance matching using the T-match
Figure 3.13 Intuitive inductor-based circuit model for the T-match
Figure 3.14 New inductor-based circuit model of the T-match dipole
Figure 3.18 Return loss for circuit with f0 = 897 MHz, β = 0.165
Figure 3.19 Return loss for circuit with f0 = 890 MHz, β = 0.17
Figure 3.20 Circuit predicted impedance looking into antenna
Figure 3.26 Tag operating above a ground plane, shown with image
Figure 3.27 Impedance of a near-resonant dipole above a 300 mm2 ground plane
Figure 3.28 Microstrip antenna fed by a microstrip transmission line
Figure 3.30 Traditional unbalanced way to feed the microstrip antenna top bottom
Figure 3.33 Impedance of variable length dipole in free space (left) and 3.2 mm separation from an infinite metal ground plane (right)
Figure 3.37 Circuit model of combined dipole / microstrip antenna functioning in air
Figure 3.38 Circuit model of combined dipole / microstrip antenna functioning on metal
Figure 3.40 (a) Power transfer efficiency of combined dipole / microstrip antenna in air
Figure 3.40 (b) Power transfer efficiency of combined dipole / microstrip antenna on metal (b).