On the Miniaturization of Semiplanar Chiral Metamaterial Structures

In this paper, miniaturized chiral metamaterial (CMM) structures with smaller unit cells or lower resonant frequencies are investigated. In achieving this purpose, three general ideas are proposed: using dendritic fractal geometry, using some wideband antenna designs, and utilizing echelon meandered structures. Based on these methods, some miniaturized CMM structures with giant optical activity and negative refraction indices are proposed for the right and left circularly polarized waves, and their effective parameters are retrieved. The proposed structures possess smaller unit cell sizes and some of them exhibit considerable optical activity compared with similar CMM designs; thus, they can be used as ultrathin microwave polarization rotators.