Periodic finite-difference time-domain analysis of loaded transmission-line negative-refractive-index metamaterials

In this paper, a systematic methodology is proposed for the full-wave time-domain analysis of planar loaded transmission-line (TL)-based negative-refractive-index (NRI) media. Lumped inductors and capacitors are incorporated in a finite-difference time-domain (FDTD) mesh via an "extended FDTD" approach, combining Maxwell\´s equations with lumped-element voltage-current characteristics. The analysis is facilitated by periodic boundary conditions that restrict the simulated domain to a single unit cell of the periodic loaded TL grid. Thus, fast numerical characterization of the NRI structures under study is attained. The proposed technique is successfully compared to measured results and is proven to consist of an effective tool for the rigorous explanation of experimental observations through the dispersion analysis and computation of modal patterns and relative strengths of the types of waves supported by an NRI medium.