Effective-Medium Properties of Cylindrical Transmission-Line Metamaterials

This letter presents a cylindrical negative-refractive-index transmission-line (NRI-TL) metamaterial composed of radially oriented NRI-TL layers. This arrangement introduces radially inhomogeneous and anisotropic effective permeability and permittivity, whose profiles may be extracted from full-wave simulations using a discrete multilayer approximation. It is shown that a cylindrical NRI-TL metamaterial of single-unit-cell thickness may be described as a homogeneous, anisotropic effective medium exhibiting resonances akin to those observed in isotropic cylindrical structures, which may be used to enhance the radiated power of nearby antennas. An analytical formulation describing the near fields, radiation patterns, and power-ratio enhancement displays very good agreement with full-wave simulations.