Design of multiple FSS screens with dissimilar periodicities for directivity enhancement of a dual-band patch antenna

A novel design for a multiple frequency selective surface (FSS) screens with dissimilar periodicities for directivity enhancement of a conventional dual-band patch antenna is presented. In the proposed new design, two square-loop arrays with different periodicity are placed above and below a thin dielectric layer. Using an efficient cascading procedure, several important parameters that characterize the thin FSS superstrate are investigated, and an optimal FSS array sizes was obtained. The directivity and radiation of an FSS antenna composite at two operating frequencies has been simulated. The results show that the proposed thin FSS superstrate yields 9.1 and 7.88 dB directivity enhancements at 7.9 GHz and 11.38 GHz, respectively, as compared to that of a patch antenna (5.91 dB, 4.47 dB), while its height is only one half of that of a conventional patch antenna and the thickness is only about 0.1λ.