A three-dimensional isotropic transmission-line metamaterial topology for free-space excitation

This work proposes a three-dimensional isotropic transmission-line metamaterial topology for free-space excitation whose negative-refractive-index properties are validated by full-wave simulation. The topology is based on a physical realization of the symmetrical condensed node of transmission-line matrix modeling, but reverses the positions of the inductive and capacitive lumped elements in order to yield an isotropic negative refractive index and good matching to free space.