Analysis of frequency selective surfaces on chiral slab

In this thesis a new type Frequency Selective Surface (FSS), named Chiro-FSS, is analysed. A Chiro-FSS is comprised of two dimensional infinite periodic array of conducting elements printed on an isotropic chiral slab. The spectral characteristics of Chiro-FSS consisting of various geometries of conducting elements are examined in detail. In the analysis, the modal technique which is employed in the analysis of FSS printed on a dielectric substrate (conventional FSS) is used, since the existence of the isotropic chiral slab does not alter the transversal nature of the problem. In a chiral medium only left circularly polarised (LCP) and right circularly polarised (RCP) plane waves can propagate. Therefore the transversal components of the scattered electric and magnetic fields are expressed as the infinite sums of LCP and RCP, TE and TM Floquet modes propagating in the chiral slab and in the surrounding medium, respectively. These Floquet modes also satisfy the periodicty requirements imposed by the geometry. Boundary conditions combined with the orthogonal property of the Floquet modes over a single unit cell leads to an integral equation for the unknown current density induced iiion a conducting element by the incident plane wave. The resulting integral equation is then solved by Method of Moments (MOM), thereby expressing the current distribution on a conducting element by suitable basis functions. Upon finding the unknown current coefficients by means of matrix inversion, the reflection and transmission coefficients of the Chiro-FSS are computed. Computed resuts of the reflection and transmission characteritics of five different type of Chiro-FSS comprised of conducting elements shaped as, narrow strips, cross dipoles, circular rings, square loops and square patches are presented.Key words : frequency selective surface, chiral.