| This thesis proposes a transmission-line approach to the design of left-handed media that exhibit a negative refractive index based on the periodic reactive loading of a host transmission line medium in a dual (high-pass) configuration. A practical two-dimensional implementation of these metamaterials using a microstrip host medium is proposed, and the essential features of the dispersion characteristic are obtained using periodic analysis, including expressions for a negative effective permittivity and permeability. These ideas are then applied to the design of planar structures for microwave circuit and full-wave simulation, and negative refraction and focusing at a planar interface are verified. Experimental results for two experimental prototypes demonstrate focusing and dispersion characteristics in excellent correspondence with theory and simulations. These results represent the first experimental verification of focusing at a planar interface by virtue of a negative refractive index, and depict extremely large bandwidths over which the refractive index remains negative. |
