An integrated compact circular-polarized annular ring slot antenna is proposed in this paper. It consists of an annular ring slot radiator and a hybrid patch coupler. The hybrid patch coupler is integrated with the annular ring slot antenna to radiate the circular-polarized wave, while size of the antenna remains the same. Both the impedance bandwidth and axial ratio bandwidth of the proposed design almost cover the entire UHF band of RFID system and it has the features of easy fabrication and low cost. To verify the proposed design, a prototype is fabricated. Measured results agree well with the simulated results.
2. 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, 365-385, 2012.
3. Tiang, J.-J., M. T. Islam, N. Misram, and J. S. Mandeep, "Circular microstrip slot antenna for dual-frequency RFID application," Progress In Electromagnetics Research, Vol. 120, 499-512, 2011.
4. Wong, K. L., C. C. Huang, and W. S. Chen, "Printed ring slot antenna for circular polarization," IEEE Trans. Antennas Propag., Vol. 50, No. 1, 75-55, Jan. 2002.
5. Chen, W. S., C. C. Huang, and K. L. Wong, "Microstrip-line-fed printed shorted ring-slot antennas for circular polarization," Microw. Opt. Technol. Lett., Vol. 31, 137-140, Oct. 2001.
6. Chang, T. N. and C. P. Wu, "Microstripline-fed circularly-polarized aperture antenna," IEEE AP-S Int. Symp. Dig., 1372-1375, 1998.
7. Soliman, E. A., W. De Raedt, and G. A. E. Vandenbosch, "Circularly polarized slot antenna dual-fed with microstrip lines," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 16, 2259-2267, 2008.
8. Qing, X. M. and Y. W. M. Chia, "Circularly polarized circular ring slot antenna fed by stripline hybrid coupler," Electronics Letters, Vol. 35, No. 25, 2154-2155, Dec. 1999.
9. Li, Y., S. Sun, L. J. Jiang, and T. T. Ye, "A circular polarization hybrid-integrated rectangular ring antenna for RFID reader," IEEE Int. Symp. on Antennas and Propag., 1-2, Jul. 8-14, 2012.
10. Sadat, S., M. Fardis, F. Geran, and G. Dadashzadeh, "A compact microstrip square-ring slot antenna for UWB applications," Progress In Electromagnetics Research, Vol. 67, 173-179, 2007.
11. Yu, A., F. Yang, and A. Elsherbeni, "A dual band circularly polarized ring antenna based on composited right and left handed metamaterials," Progress In Electromagnetics Research, Vol. 78, 73-81, 2008.
12. Sze, J. Y., T. H. Hu, and T. J. Chen, "Compact dual-band annular-ring slot antenna with meandered ground plane," Progress In Electromagnetics Research, Vol. 95, 299-308, 2009.
13. Sze, J.-Y. and S.-P. Pan, "Design of broadband circularly polarized square slot antenna with a compact size," Progress In Electromagnetics Research, Vol. 120, 513-533, 2011.
14. Chew, W. C., "A broad-band annular-ring microstrip antenna," IEEE Trans. Antennas Propag., Vol. 30, No. 5, 918-922, Sep. 1982.
15. Sun, S. and L. Zhu, "Miniaturized patch hybrid couplers using asymmetrically loaded cross slots," IET Microw. Antennas Propag., Vol. 4, No. 9, 1427-1433, Sep. 2010.