This paper presents a method of antenna impedance measurement for RFID tag antenna based on a differential probe. The importance of accurate impedance measurement in optimal design of tag antenna, especially for the metal tags, is first addressed. Afterwards, an overview of the existing methods based on the singleended probe and the balun probe is presented. The proposed method using the differential probe is explained based the well-known two port network model. Experiments for both balanced and unbalanced tag antenna measurement demonstrate the differential probe can provided better agreement with simulated results.
2. Kim, D.-Y. and J.-G. Yook, "Interference analysis of UHF RFID systems," Progress In Electromagnetics Research B, Vol. 4, 115-126, 2008.
3. Shi, X.-L., X.-W. Shi, Q.-L. Huang, and F. Wei, "An enhanced binary anti-collision algorithm of backtracking in RFID system," Progress In Electromagnetics Research B, Vol. 4, 263-271, 2008.
4. Ng, M. L., K. S. Leong, and P. H. Cole, Design and miniaturization of an RFID tag using a simple rectangular patch antenna for metallic object identification, IEEE Antennas and Propagation Society International Symposium, 1741-1744, Hawaii, USA, 2007.
5. Park, Y., S. Lee, J. Kang, and Y. C. Chung, Various UHF RFID tag for metallic object, IEEE Antennas and Propagation Society International Symposium, 2285-2288, Hawaii, USA, 2007.
6. Ukkonen, L., 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," IEEE Antennas and Wireless Propagation Letters, Vol. 5, No. 1, 414-417, 2006.
7. Choi, W., H. W. Son, J.-H. Bae, G. Y. Choi, C. S. Pyo, and J.-S. Chae, "An RFID tag using a planar inverted-F antenna capable of being stuck to metallic objects," ETRI Journal, Vol. 28, No. 2, 2006.
8. Hirvonen, M., P. Pursula, K. Jaakkola, and K. Laukkanen, "Planar inverted-F antenna for radio frequency identification," Electronic Letters, Vol. 40, No. 14, 2004.
9. Ng, M. L., K. S. Leong, and P. H. Cole, A small passive UHF RFID tag for metallic item identification, International Technical Conference on Circuits/Systems, Computers and Communications, 10-13, Chiang Mai, Thailand, 2006.
10. Loo, C.-H., K. Elmahgoub, F. Yang, A. Elsherbeni, D. Kajfez, A. Kishk, T. Elsherbeni, L. Ukkonen, L. Sydnheimo, M. Kivikoski, S. Merilampi, and P. Ruuskanen, "Chip impedance matching for UHF RFID tag antenna design," Progress In Electromagnetics Research, Vol. 81, 359-370, 2008.
11. Stutzman, W. L. and G. A. Thiele, Antenna Theory and Design, John Wiley & Sons, 1998.
12. Leong, K. S., M. N. Mg, and P. H. Cole, Investigation of RF cable effect on RFID tag antenna impedance measurement, IEEE Antennas and Propagation Society International Symposium, 573-576, Hawaii, USA, 2007.
13. Eunni, M. B., A novel planar microstrip antenna design for UHF RFID, M.S. Thesis, University of Kansas, 2006.
14. Camp, M., R. Herschman, T. Zelder, and H. Eul, "Determination of the input impedance of RFID transponder antennas with novel measurement procedure using a modified on-wafer-prober," Advances in Radio Science, Vol. 5, 115-118, 2007.
15. Yang, Z. Q., T. Yang, and Y. Liu, "Aanalysis and design of a reduced-size marchand balun," Journal of Electromagnetic Waves and Applications, Vol. 21, No. 9, 1169-1175, 2007.
16. Dobkin, D. M. and S. M. Weigand, Environmental effects on RFID tag antennas, Microwave Symposium Digest, 2005 IEEE MTT-S International, 2005.
17. Palmer, K. D. and M. W. Rooyen, "Simple broadband measurements of balanced loads using a network analyzer," IEEE Transactions on Instrumentation and Measurement, Vol. 55, No. 1, 266-272, 2006.
18. Fan, W., A. Lu, L. L. Wai, and B. K. Lok, Mixed-mode S-Sparameter characterization of differential structures, Electronics Packaging Technology, 5th Conference, 533-537, 2003.
19. Single-ended and differential S-parameters, MAXIM application note, hfan-5.1.0.
20. Elsadek, H. and D. Nashaat, "Ultra mimiturized E-shaped dual band PIFA on cheap foam and FR4 substrate," Journal of Electromagnetic Waves and Applications, Vol. 20, No. 3, 291-300, 2006.
21. Zhang, M. T., Y. B. Chen, Y. C. Jiao, and F. S. Zhang, "Dual circularly polarized antenna of compact structure for RFID application," Journal of Electromagnetic Waves and Applications, Vol. 20, No. 14, 1895-1902, 2006.
22. Sim, C. Y. D., "A novel dual frequency PIFA design for ease of manufacturing," Journal of Electromagnetic Waves and Applications, Vol. 21, No. 3, 409-419, 2007.
23. Elsadek, H. and D. Nashaat, "Quad band compact size trapezoidal PIFA antanna," Journal of Electromagnetic Waves and Applications, Vol. 21, No. 7, 865-876, 2007.
24. Khodaei, G. F., J. Nourinia, and C. Ghobadi, "A practical miniaturized U-slot patch antenna with enhanced bandwidth," Progress In Electromagnetics Research B, Vol. 3, 47-62, 2008.
25. Abbaspour, M. and H. R. Hassani, "Wideband star-shaped microstrip patch antenna," Progress In Electromagnetics Research Letters, Vol. 1, 61-68, 2008.
26. Jolani, F. and A. M. Dadgarpour, "Compact M-slot folded patch antenna for WLAN," Progress In Electromagnetics Research Letters, Vol. 3, 35-42, 2008.
27. Mahmoud, S. F. and A. F. Sheta, "Cavity mode analysis for a rectangular patch with a shorting pin," Journal of Electromagnetic Waves and Applications, Vol. 20, No. 14, 2013-2025, 2006.