鑑於無線辨識系統(RFID)之發展趨於成熟及應用日漸普遍，本論文提出一 RFID 標籤天線之設計方法，係採用偶極天線架構及多重電感性圓環之匹配網 路，由於 RFID 標籤天線在應用上需搭配微晶片使用，而微晶片之阻抗通常並非 常用的 50 歐姆，視不同的廠牌與型號各有不同的阻抗，較常見的為一小實部及 電容性虛部，而 RFID 標籤天線必須依照所欲搭載之微晶片，針對其阻抗做共軛 匹配，因此阻抗匹配乃 RFID 天線之設計重點，本論文提出一調整天線輸入阻抗 之匹配網路，即利用多重電感性圓環結構，先調整第一圈電感性圓環之大小決定 天線輸入阻抗虛部值，再利用增加電感性圓環之方式調整實部阻抗值，藉由多重 電感性圓環來實現天線實虛部阻抗可獨立調整之機制，在適用本論文所採用之微 晶片時可達到良好之匹配與寬頻之頻寬，而當天線欲搭載不同阻抗值之微晶片 時， 利用相同的方法可調整天線輸入阻抗至所需匹配的值，因此本論文之設計 亦可適用於其他不同廠牌型號之微晶片。
在對稱性 RFID 天線輸入阻抗之量測上，需注意使用平衡式饋入的方式以降 低量測上之不準度，本論文亦提供一量測之方法與設定，利用 balun 與兩條同軸 線將非平衡之同軸接頭轉換為平衡之雙導線結構，並將量測參考平面校正至雙導 線最前端，此外，饋入天線時亦需考慮電磁耦合的效應，建議將饋入線與天線保 持垂直以使電磁耦合的效應降至最小。
本論文所提出 RFID 天線之設計與阻抗匹配方法及量測方法，於特性及適用 範圍上皆有不錯的表現，希望對無線通訊產業及 RFID 系統的應用上能有所助益。
49
參考文獻
[1] L. Ukkonen, M. Schaffrath, D.W. Engels, L. Sydanheimo, and M. Kivikoski,
“Operability of Folded Microstrip Patch-Type Tag Antenna in the UHF RFID Bands Within 865-928 MHz,” Antennas Wirel. Propag. Lett., vol. 5, no. 1, pp.
414-417, Dec. 2006.
[2] G. Marrocco, A. Fonte, and F. Bardati, “Evolutionary design of miniaturized meander-line antennas for RFID applications,” in Proc. IEEE Antennas and
Propag. Soc. Int. Symp., vol. 2, pp. 362-365, 16-21 June 2002.
[3] C. T. Rodenbeck, “Planar miniature RFID antennas suitable for integration with batteries,” IEEE Trans. Antennas Propag.,, vol. 54, no. 12, pp. 3700-3706, Dec.
2006.
[4] H.-W. Son and C.-S. Pyo, “Design of RFID tag antennas using an inductively coupled feed,” Electronics Letters, Volume 41, Issue 18, pp. 994 – 996, 1 Sept.
2005.
[5] W. Choi, H.W. Son, C. Shin, J.-H. Bae, and G. Choi, “RFID tag antenna with a meandered dipole and inductively coupled feed,” in Proc. IEEE Antennas and
Propag. Soc. Int. Symp., pp. 619 – 622, 9-14 July 2006.
[6] L. Yang, S. Serkan Basat, and M.M. Tentzeris, “Design and development of novel inductively coupled RFID antennas,” in Proc. IEEE Antennas and Propag.
Soc. Int. Symp., pp. 1035 – 1038, 9-14 July 2006.
[7] H. Choo and H. Ling, “Design of electrically small planar antennas using inductively coupled feed,” Electronics Letters, Volume 39, Issue 22, pp. 1563 – 1565, 30 Oct. 2003.
[8] K.V.S. Rao, P.V. Nikitin, and S.F. Lam, “Antenna design for UHF RFID tags: a review and a practical application,” IEEE Transactions on Antenna and
Propagation, Volume 53, Issue 12, pp. 3870 – 3876, Dec. 2005.
50
[9] C. Cho, H. Choo, and I. Park, “Broadband RFID tag antenna with quasi-isotropic radiation pattern,” Electronics Letters, Volume 41, Issue 20, pp. 1091 – 1092, 29 Sept. 2005.
[10] C. Cho, H. Choo, and I. Park, “Design of Novel RFID Tag Antennas for Metallic Objects,” in Proc. IEEE Antennas and Propag. Soc. Int. Symp., pp. 3245 – 3248, 9-14 July 2006.
[11] W. Lee, K. Chang, and Y.J. Yoon, “Small RFID tag antenna with bandwidth enhanced characteristic,” in Proc. IEEE Antennas and Propag. Soc. Int. Symp., pp. 1359 – 1362, 9-14 July 2006.
[12] B. Yang and Q. Feng, “A folded dipole antenna for RFID tag,” International
Conference on Microwave and Millimeter Wave Technology, Volume 3, pp. 1047
- 1049, 21-24 April 2008.[13] Y. Feng, B. Braaten, and R. Nelson, “Analytical expressions for small loop antennas - with applicaton to EMC and RFID systems,” IEEE International
Symposium on Electromagnetic Compatibility, Volume 1, pp. 63 - 68, 14-18 Aug.
2006.
[14] H.-K. Ryu and J.-M. Woo, “Size Reduction in UHF Band RFID Tag Antenna Based on Circular Loop Antenna,” International Conference on Applied
Electromagnetics and Communications, pp. 1 – 4, 12-14 Oct. 2005.
[15] A.S. Andrenko, M. kai, T. Maniwa, and T. Yamagajo, “Compact printed-on-CD UHF RFID tag antennas,” in Proc. IEEE Antennas and Propag. Soc. Int. Symp., pp. 5455 – 5458, 9-15 July 2007.
[16] Y. Okano, “A simple shape broadband planar antenna adaptable to RFID-tag,”
IEEE Transactions on Antenna and Propagation, Volume 54, Issue 6, pp. 1885 –
1888, June 2006.[17] G. Marrocco, “RFID Antennas for the UHF Remote Monitoring of Human Subjects,” IEEE Transactions on Antenna and Propagation, Volume 55, Issue 6, Part 2, pp. 1862 – 1870, June 2006.
51
[18] W.L. Stutzm and G.A. Thiele, “Antenna Theory and Design,” 2
nd
, John Wiley, New York, 1998.[19] D.M. Pozar, “Microwave Engineering,” 3
rd
, John Wiley, New York, 2003.[20] Finkenzeller, “RFID Handbook,” Wuket, 2000.
[21] C.C. Chang and Y.C. Lo, “Broadband RFID tag antenna with capacitively coupled structure,” Electronics Letters, Volume 42, Issue 23, pp. 1322 – 1323, 9 Nov. 2006.
[22] G. Marrocco, A. Fonte, and F. Bardati, “Evolutionary design of miniaturized meander-line antennas for RFID applications,” in Proc. IEEE Antennas and
Propag. Soc. Int. Symp., Volume 2, pp. 362 – 365, 16-21 June 2002.
[23] C.H. Cheng and R.D. Murch, “Asymmetric RFID tag antenna,” in Proc. IEEE