Anisotropic Transmission-Line Metamaterials for 2-D Transformation Optics Applications

In this contribution, we present a two-dimensional metamaterial unit cell which synthesizes effective material parameters needed for "transformation optics" applications. The metamaterial consists of a grid of reactively loaded transmission-line segments and is a generalization of a previously presented unit cell in that it also synthesizes off-diagonal elements of the permeability tensor. We apply this unit cell to two "transformation optics" applications, a retrodirective reflector, and a cloak. This cloak is different from the so-far reported split-ring-resonator/wire structures in that it not only synthesizes the required mu(rho) and epsilon(z) distribution but also the mu(phi) one. For the cloak, detailed radar cross-section (RCS) and bandwidth results are presented. It is shown that the total RCS bandwidth is 33.5%, and that losses influence the cloaking performance not critically, pointing to the possibility of practical "transformation optics" designs using the proposed unit cell. Full-wave simulation results of a transmission-line metamaterial cloak in microstrip technology are presented, verifying that the unit cell presented in this paper synthesizes the effective material parameters needed for "transformation optics" or applications that require effective material parameters with off-diagonal tensor elements.