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Design and Fabrication of Flexible Near-field UHF Tags Antennas for Metallic Objects J. M. Huang, Z. Q. Wu, J. N . Jhou, C. H . Wen, C. W. Lin, C. Y. Liang and Y. S. Yeh Department of Electro-Optical Engineering Southern Taiwan University 1 Nan-Tai St., Yung-Kung City, Tainan County, Taiwan, 710 Abstract 研究方向 The readability of near-field RFID tags is less dependent on the material of the product, the storage method of the product, the characteristics of the tag and the quality of the reader. However, near-field RFID label fabricated tags usually do not work attached to metal because there are eddy currents on the metallic surface. Many tags attached to metal are not flexible and are expensive in cost. In the project, tags with the SRR (Split Ring Resonator) antennas are developed. It is possible to use the tags with the SRR antennas on the metal to enhance the effective magnetic permeability. B. Tags with SRR antennas I.THEORY Antenna structure [1] 1 f0 2 Ls Cs eff ( ) 1 0 2 2 Voc H z NS Cs is the series connexion of the capacities Ls is the total inductance where ω=2πf , ωo=2πfo , F=π(a/p)2 a is the inner radius of the SRR p is the periodicity of the structure S11 S11 Z Z read distance : 0 cm (b) carve machine read distance : 11 cm C. Novel tag with a SRR antenna where Voc is the open-circuit voltage μ is the magnetic permeability ω is the angular frequency HZ is the magnetic field transversal to the SRR N is the number of turns S is the SRR area II. EXPERIMENTAL DEVICE (a) Network analyzer (b) Tag on metal Equivalent circuit model of the SRR[2] where F 2 (a) Tag on metal Tag Experimental Tag on metal (a) Tag on lron (b) Tag on Aluminum S11 S11 Z Z (d) CSL reader read distance : 35 cm ， read distance : 10 cm III. RESULTS AND DISCUSSION V. CONCLUSION A. Tag with loop antennas (a) Tag on metal S11 (b) Tag with PET on metal S11 Z Reference Z read distance : 0 cm Near-field RFID label fabricated tags usually do not work attached to metal because there are eddy currents on the metallic surface. In the project, tags with the SRR (Split Ring Resonator) antennas are developed. It is possible to use the tags with the SRR antennas on the metal to enhance the effective magnetic permeability. Experiment measuring reading distance 35 cm. A 3D-FEM code (Ansoft HFSS) is applied to analyze the characteristics of the patch antenna in this study. The code is provided by the National Center for High-Performance Computing (NCHC). This project is financially sponsored by National Science Council (grand no. NSC 97-2622-E218006-CC3). read distance : 4 cm 1. J. B. Pendry, A. J. Holden, D. J. Robbins, and W. J. Stewart , “Magnetism from Conductors and Enhanced Non-Linear Phenomena,” IEEE Transactions on Microwave Theory and Techniques, vol. 47,No. 11,Nov. 1999. 2. J. Dacuña , R. Pous , “Near-field UHF tags based on metamaterials concepts.” BRIDGE , 11 July 2007.