A novel broadband circularly polarized slot antenna with a rotated slot for bandwidth enhancement is proposed. The antenna has a simple structure, consisting of a microstrip feed line, a substrate, and a rotated rectangular slot with two branches etched on the plane. By appropriately adding the rotated rectangular slot and two branches on the ground-plane, the impedance bandwidth of the antenna is enlarged, and its wide axial-ratio (AR) bandwidth is achieved. Experimental results show the proposed antenna has good right-hand circular polarization (RHCP) characteristics. The measured -10-dB return loss impedance bandwidth and 3 dB axial-ratio bandwidth are 38.8% (1.5 GHz~2.2 GHz) and 25.6% (1.56 GHz~2.02 GHz) at the center frequency of 1.8 GHz.
2. Seng, L.-Y. T. and T.-Y. Han, "Microstrip-fed circular slot antenna for circular polarization," Microwave Opt. Technol. Lett., Vol. 50, No. 4, 1056-1058, Apr. 2008.
3. Chang, T.-N. and J.-M. Lin, "Circularly polarized antenna having two linked slot-rings," IEEE Trans. Antennas Propag., Vol. 59, No. 8, 3057-3060, Aug. 2011.
4. Iwasak, H., "A circularly polarized small-size microstrip antenna with a cross slot," IEEE Trans. Antennas Propag., Vol. 44, No. 10, 1399-1401, Oct. 1996.
5. Sudha, T., T. S. Bedavathy, and N. Bhat, "Wideband single-fed circularly polarized patch antenna," Electronics Letters, Vol. 40, No. 11, 648-649, May 2004.
6. Lee, J. H. and J. M. Woo, "Design of a L-type aperture coupled circular polarization patch antenna with a single feed," Proc. 5th Antennas, Propag. EM Theory Int. Symp., 14-17, Beijing, China, Aug. 2000.
7. Mak, K.-M. and K.-M. Luk, "A circularly polarized antenna with wide axial ratio beamwidth," IEEE Trans. Antennas Propag., Vol. 57, No. 10, 3309-3312, Oct. 2009.
8. Targonski, S. D. and D. M. Pozar, "Design of wideband circularly polarized aperture coupled microstrip antennas," IEEE Trans. Antennas Propag., Vol. 41, No. 2, 214-220, Feb. 1993.
9. Pozar, D. M. and S. M. Duffy, "A dual-band circularly polarized aperture-coupled stacked microstrip antenna for global positioning satellite," IEEE Trans. Antennas Propag., Vol. 45, No. 11, 1618-1625, Nov. 1997.
10. Pan, M. C. and K. L. Wong, "Broadband circularly polarized microstrip antenna with a dual-perpendicular feed," Microwave Opt. Technol. Lett., Vol. 24, No. 6, 420-422, Mar. 2000.
11. Ushijima, Y., S. Feng, E. Nishiyama, and M. Aikawa, "A novel circular polarization switchable slot-ring array antenna with orthogonal feed circuit," 2008 Asia-Pacific Microwave Conference (APMC), 1569-1572, 2010.
12. Jan, J.-Y. and J.-W. Su, "Bandwidth enhancement of a printed wide-slot antenna with a rotated slot," IEEE Trans. Antennas Propag., Vol. 53, No. 6, 2111-2114, Jun. 2005.