In this paper, a dual-fed circularly polarized antenna design with high isolation is presented for radio frequency identification(RFID) reader. The proposed antenna is excited by two fed ports connected with a circular split-ring microstrip line underneath the ground plane. A radial aperture in the ground plane provides coupling between the split-ring microstrip and radiating patch. For multiple RFID band requirements, the dimension of the aperture can be modified to obtain high isolation on different RFID Band. Finally, an antenna prototype for China RFID Band(920-925 MHz) is fabricated. The measured results agree well wit13h simulation, and show 10-dB matching bandwidth of 18%(820-1000 MHz), 3-dB axial ratio(AR) bandwidth of 11%(854-960 MHz), and 25-dB isolation bandwidth of 11 MHz(917-928 MHz).
2. Chen, X., G. Fu, S. X. Gong, Y. L. Yan, and W. Zhao, "Circularly polarized stacked annular-ring microstrip antenna with integrated feeding network for UHF RFID readers," IEEE Antennas and Wireless Propagation Letters, Vol. 9, 542-545, Jun. 2010.
3. Deng, J.-Y., L.-X. Guo, T.-Q. Fan, Z.-S. Wu, Y.-J. Hu, and J.-H. Yang, "Wideband circularly polarized suspended patch antenna with indented edge and gap-coupled feed," Progress In Electromagnetics Research, Vol. 135, 151-159, 2013.
4. Wang, P., G. Wen, J. Li, Y. Huang, L. Yang, and Q. Zhang, "Wideband circularly polarized UHF RFID reader antenna with high gain and wide axial ratio beamwidths," Progress In Electromagnetics Research, Vol. 129, 365-358, 2012.
5. Tiang, J.-J., M. T. Islam, N. Misran, and J. S. Mandeep, "Circular microstrip slot antenna for dual-frequency RFID application," Progress In Electromagnetics Research, Vol. 120, 499-512, 2011.
6. Chang, T. N. and J. M. Lin, "Circularly polarized ring-patch antenna," IEEE Antennas and Wireless Propagation Letters, Vol. 11, 26-29, 2012.
7. Ooi, P. C. and K. T. Selvan, "A dual-band circular slot antenna with an offset microstrip-FED line for PCS, UMTS, IMT-2000, ISM, bluetooth, RFID and WLAN applications," Progress In Electromagnetics Research Letters, Vol. 16, 1-10, 2010.
8. Fan, Z., S. Qiao, J. T. Huang-Fu, and L.-X. Ran, "Signal descriptions and formulations for long range UHF RFID readers," Progress In Electromagnetics Research, Vol. 71, 109-127, 2007.
9. Kim, D.-Y., H.-G. Yoon, B.-J. Jang, and J.-G. Yook, "Interference analysis of UHF RFID systems," Progress In Electromagnetics Research B, Vol. 4, 115-126, 2008.
10. Lazaro, A., D. Girbau, and R. Villarino, "Effects of interferences in UHF RFID systems," Progress In Electromagnetics Research, Vol. 98, 425-443, 2009.
11. Lim, W. G., S. Y. Park, and W. I. So, "RFID reader front-end having robust Tx leakage canceller for load variation," IEEE Transactions on Microwave Theory and Techniques, Vol. 57, No. 5, 1348-1355, 2009.
12. Bae, J.-H., W.-K. Choi, J.-S. Kim, G.-Y. Choi, and J.-S. Chae, "Study on the demodulation structure of reader receiver in a passive RFID environment," Progress In Electromagnetics Research, Vol. 91, 243-258, 2009.
13. Kim, W. K., W. Na, and J. W. Yu, "A high isolated coupled-line passive circulator for UHF RFID reader," Microwave and Optical Technology Letters, Vol. 50, No. 10, 5297-2600, 2008.
14. Mireles, E. and S. K. Sharma, "A novel wideband circularly polarized antenna for worldwide UHF band RFID reader applications," Progress In Electromagnetics Research B, Vol. 42, 23-44, 2012.
15. Jung, Y. K. and B. Lee, "Dual-band circularly polarized microstrip RFID reader antenna using metamaterial branch-line coupler," IEEE Transactions on Antennas and Propagation, Vol. 60, No. 2, 786-791, 2012.
16. Secmen, M. and A. Hizal, "A dual-polarized wide-band patch antenna for indoor mobile communication applications," Progress Progress In Electromagnetics Research, Vol. 100, 189-200, 2010.
17. Yao, Y., X. Wang, X. D. Chen, J. S. Yu, and S. H. Liu, "Novel diversity/MIMO PIFA antenna with broadband circular polarization for multimode satellite navigation," IEEE Antennas and Wireless Propagation Letters, Vol. 11, 65-68, 2011.
18. Vongsack, S., C. Phongcharoenpanich, S. Kosulvit, K. Hamamoto, and T. Wakabayashi, "Unidirectional antenna using two-probe excited circular ring above square reflector for polarization diversity with high isolation," Progress In Electromagnetics Research, Vol. 133, 159-176, 2013.
19. Xie, J.-J., Y.-Z. Yin, J. Ren, and T. Wang, "A wideband dual-polarized patch antenna with electric probe and magnetic loop feeds," Progress In Electromagnetics Research, Vol. 132, 499-515, 2012.
20. Segovia-Vargas, D., F. J. Herraiz-Martinez, E. Ugarte-Munoz, L. E. Garcia-Munoz, and V. Gonzalez-Posadas, "Quad-frequency linearly-polarized and dual-frequency circularly-polarized microstrip patch antennas with CRLH loading," Progress In Electromagnetics Research, Vol. 133, 91-115, 2013.
21. Liu, C., J.-L. Guo, Y.-H. Huang, and L.-Y. Zhou, "A novel dual-polarized antenna with high isolation and low cross polarization for wireless communication," Progress In Electromagnetics Research Letters, Vol. 32, 129-136, 2012.
22. Krairiksh, M., P. Keowsawat, C. Phongcharoenpanich, and S. Kosulvit, "Two-probe excited circular ring antenna for MIMO application," Progress In Electromagnetics Research, Vol. 97, 417-431, 2009.
23. Wu, G.-L., W. Mu, G. Zhao, and Y.-C. Jiao, "A novel design of dual circularly polarized antenna FED by L-strip," Progress In Electromagnetics Research, Vol. 79, 39-46, 2008.
24. Chou, H.-T., H.-C. Cheng, H.-T. Hsu, and L.-R. Kuo, "Investigations of isolation improvement techniques for multiple input multiple output (MIMO) WLAN portable terminal applications," Progress In Electromagnetics Research, Vol. 85, 349-366, 2008.
25. 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.
26. Chang, T. N. and J. M. Lin, "A novel circularly polarized patch antenna with a serial multislot type of loading," IEEE Transactions on Antennas and Propagation, Vol. 55, No. 11, 3345-3348, 2007.
27. Paret, D., RFID at Ultra and Super High Frequencies Theory and Application, 2nd Edition, Wiley, United Kingdom, 2009.
28. , , , Online available: http://www.tek.com/sites/tek.com/files/media /media/resources/37W 18864 2.pdf.
29. , , , Online available: http://www.rfidinfo.jp/whitepaper/379.pdf.