A broadband CPW-fed circularly polarized square slot antenna for ultra-high-frequency (UHF) radio frequency identification (RFID) applications is proposed. It consists of a square slot embedded with a spur line along diagonal and an F-shaped feeding structure. The proposed antenna achieves an imped-ance bandwidth about 307 MHz (34.6% @886 MHz) and a 3 dB axial ratio (AR) bandwidth about 232MHz (24.3% @954 MHz). The 3 dB AR beam-width is about 96 degrees over the UHF band of 840-960 MHz. The proposed reader antenna based on CPW structure is easy to integrate. With the symmetry and bidirectional radiation pattern, there are less readers needed in some applications, such as access con-trol, than the reader with unidirectional pattern, which will definitely decrease the implemented cost. Therefore, this universal design with desired performance across the entire UHF RFID band (from 840 MHz to 960 MHz) can be applied to all the UHF RFID applications worldwide. Detailed considera-tions of the design and main parameters will be studied in this paper.
2. Want, R., "An introduction to RFID technology," IEEE Pervasive Comput., Vol. 5, No. 1, 25-33, Jan.-Mar. 2006.
3. Finkenzeller, K., RFID Handbook, 2nd Ed., Wiley, New York, 2004.
4. 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.
5. Chen, S.-L., S.-K. Kuo, and C.-T. Lin, "A metallic RFID tagdesign for steel-bar and wire-rod management application in thesteel industry," Progress In Electromagnetics Research, Vol. 91, 195-212, 2009.
6. Lai, X.-Z., Z.-M. Xie, and X.-L. Cen, "Design of dual circularly polarized antenna with high isolation for RFID application," Progress In Electromagnetics Research, Vol. 139, 25-39, 2013.
7. Amin, Y., Q. Chen, L.-R. Zheng, and H. Tenhunen, "Development and analysis of flexible UHF RFID antennas for `green' electronics," Progress In Electromagnetics Research, Vol. 130, 1-15, 2012.
8. Chang, T. N. and J. M. Lin, "A novel circularly polarized patch antenna with a serial multislot type of loading," IEEE Trans. Antennas Propag., Vol. 55, 3345-3348, 2007.
9. 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.
10. 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.
11. 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.
12. 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.
13. Chen, Z., X. Qing, and L. Hang, "A universal UHF RFID reader antenna," IEEE Trans. Microw. Theory Tech., Vol. 57, 1275-1282, 2009.
14. Nasimuddin, Z. Chen and X. Qing, "Asymmetric-circular shape slotted microstrip antennas for circular polarization and rfid applications," IEEE Trans. Antennas Propag,, Vol. 58, 3821-3828, 2010.
15. Chen, J.-P., P. Hsu, and , "A spirally complementary split-ring resonators antenna for circular polarization and RFID reader application," 2012 IEEE Antennas and Propagation Society International Symposium (APSURSI), 1-2, 2012.
16. Wang, Z., S. Fang, S. Fu, and S. Jia, "Single-fed broadband circularly polarized stacked patch antenna with horizontally meandered strip for universal UHF RFID applications," IEEE Trans. Microw. Theory Tech., Vol. 59, 1066-1073, 2011.
17. Chen, H.-D., "Broadband CPW-fed square slot antennas with a widened tuning stub," IEEE Trans. Antennas Propag., Vol. 51, 1982-1986, 2003.
18. Yeh, S.-A., Y.-F. Lin, H.-M. Chen, and J.-S. Chen, "Slotline-fed circularly polarized annular-ring slot antenna for RFID reader," Asia Paci¯c Microwave Conference, APMC 2009, 618-621, 2009.
19. Lu, J.-H. and S.-F. Wang, "Planar broadband circularly polarized antenna with square slot for UHF RFID reader," IEEE Trans. Antennas Propag., Vol. 61, 45-53, 2013.