Free-Space Focusing at C-Band Using a Flat Fully Printed Multilayer Metamaterial Lens

A volumetric metamaterial lens exhibiting a negative refractive index (NRI) at C-band is designed and its free-space focusing properties are experimentally verified. The designed lens employs a multilayer geometry and its unit cells are loaded using metal-insulator-metal (MIM) capacitors and dual-arm spiral inductors in a biplanar configuration. These elements, although fully printed and without vias, provide strong reactive loading that enables a unit cell size of λ_o/11$ and allows the metamaterial´s dispersion properties to be accurately modeled in the effective-medium regime using an equivalent-circuit approach. It is also conducive to implementation at high frequencies, where surface-mount components are unusable. The focusing properties of the fabricated lens are confirmed for a band of frequencies around 5.0 GHz in an anechoic chamber using a free-space field probing system consisting of electrically small shielded-loop antennas affixed to a computer-controlled scanner.