Directivity enhancement of circular polarized patch antenna using ring-shaped frequency selective surface superstrate

In this letter, a ring-shaped frequency selective surface (FSS) superstrate is designed to enhance the directivity of a circularly polarized patch antenna by reducing the sidelobe levels. Based on the unit cell simulation, several important parameters that characterize the ring-shaped FSS superstrate are investigated, and the design procedure of the FSS superstrate is described. The FSS antenna composite is fabricated, and the maximum directivity is 18.98 dBi, while the sidelobe level is −18 dB. Furthermore, the antenna composite maintains its circular polarization characteristic quite well. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 199–201, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22084