Effective-medium properties of a fully-printed biplanar volumetric NRI-TL metamaterial lens

We characterize an improved fully-printed biplanar volumetric negative-refractive-index transmission-line (NRI-TL) metamaterial lens, which utilizes new double dual-arm spiral inductors and metal-insulator-metal capacitors as loading elements. The structure exhibits a NRI property from 3.92 GHz to 4.57 GHz. At these frequencies, the structure is shown to be isotropic and possesses a small electrical length around A₀/11. The real parts of its extracted effective relative permittivity and permeability are close to negative unity, hence, it is well-matched to free space and exhibits a real part of its refractive index near -1.