| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 101 === RFID tags embedded in a printed circuit board (PCB) have to feed themself into a limited space due to the preexisting onboard circuit elements, and for practical applications these tags have to support at least one meter reading distance. This paper employs multi-layer structure and proposes the concepts of the combination of LC resonance and energy coupling. This can effectively reduce the antenna area. In addition, this work also makes a comparison between the two kinds of LC resonators, the split ring resonator and the planar spiral resonant. The antennas presented in this paper are both implemented by the two-layer structure with the FR-4 substrate of the thickness 0.6 mm. The winding loop, on the top layer, is used for the complex-conjugate match and coupling the energy to the bottom layer to achieve RFID tag antenna size reduction purposes. While in the bottom layer the capacitance of LC resonator realized by the SRR is enhanced by adding the inter-digital capacitor tree structure at the gap of split ring. On the other hand, the planar spiral-type LC resonance in the bottom layer is present by the spiral inductance and the capacitance between the lines. The antenna radiates from the long strip which is connected directly to the spiral resonator. The proposed antenna is designed for RFID application, 922MHz~928MHz, and it occupies the footprint of 50 mm2 and has perfect complex-conjugate match. Moreover, the reading distance can still support one meter long. Therefore, this RFID tag proposed here is suitable for practical applications.
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