Characterization of a volumetric negative-refractive-index transmission-line (NRI-TL) metamaterial for incident waves from free-space

This paper describes the essential properties of a multilayered volumetric negative-refractive-index transmission-line (NRI-TL) metamaterial. A theoretical basis is provided by an intuitive transmission-line model that yields the dispersion and transmission properties of the metamaterial and accurately describes its effective permeability and permittivity. Furthermore, it is shown how the structure may be designed to exhibit an effective relative permeability and permittivity of ¿1 in free space, the conditions for realizing a perfect lens. These results are affirmed by finite-element full-wave simulations showing its corresponding phase-restoration and transmission properties for plane waves incident over a wide range of angles. Finally, experimental free-space focusing data for a fully printed slab lens prototype employing interdigitated capacitors and meandered inductors are presented at X-band.