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

Abstract

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. Index Terms-Dispersion, finite difference time domain (FDTD), negative refractive index (NRI).

Periodic FDTD analysis of leaky-wave structures and applications to the analysis of negative-refractive-index leaky-wave antennas

“…Note that these modes do not occur right after the boundary of the slow-to-fast wave region that is defined by the light line. As discussed in [21], the fast backward-wave modes close to the light line couple to the nonradiating surface waves, which follow the light line and hence do not contribute to leakage effects. The same argument holds for the fast forward-wave modes close to the light line.…”

“…A question that is naturally posed is whether such a methodology would preclude the determination of any attenuation constants involved, limiting the applicability of these techniques only to cases where . In [21], the authors applied the sine-cosine method of [14] in order to perform the dispersion analysis of the NRI medium of [4]. The part of the dispersion diagram corresponding to axial propagation (the -part of the Brillouin zone) is shown in Fig.…”

“…Finally, the determination of the real part of the propagation constant as a function of frequency is pursued in the same way as in [21].…”

“…A particular question of interest that stems from the survey of previous work in this area is whether it is possible to extract the attenuation constant of leaky-wave periodic structures from the FDTD analysis of their unit cell. This question becomes intriguing by the fact that the translation of Floquet's boundary conditions from the frequency domain (where they are naturally cast) to [22], extracted through the periodic FDTD analysis of [21], around the = 0-region. The results, for both the slow and fast waves, are in agreement with those extracted through the TL theory-based analysis of [23] and Ansoft's HFSS.…”

High Impedance Properties of Two-Dimensional Composite Right/Left-Handed Transmission Lines

“…CRLH TLs have been widely used to fabricate microwave components, such as directional couplers and leaky wave antennas [7,8]. A two-dimensional configuration for the CRLH TLs (2D CRLH TLs) has also been investigated to understand their basic properties [5,9,10].…”