NIM

Since XFDTD includes frequency-dependent dielectric and magnetic materials, it is capable of making three-dimensional calculations for double negative materials, also called negative index materials and meta-materials. Learn how XFDTD can be applied to these new materials.

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There is currently considerable interest in the electromagnetic behavior of materials that have both permittivity and permeability with negative real parts. These materials have several names including Negative Index Materials (NIM) and Double Negative Materials (DNG). This interest is based in large part on the availability of meta-materials with this characteristic. XFDTD, even though a time domain solver, has the capability to make calculations for these materials. This example illustrates this capability and presents some interesting results for these unusual materials.

While XFDTD is intended for full 3D calculations, these figures were made for a 2D geometry, which is efficient for illustrating the behavior of these materials. The geometry is shown in Figure 1. The green rectangle is the location of a 2D slab of material. The simple horn antenna is fed by a waveguide with a 30 GHz voltage source. The antenna is tilted at a 20 degree angle with the slab normal. The voltage waveform is ramped in amplitude over the first cycle. The electric field is polarized perpendicular to the plane of the figures so the magnetic field is in the plane of incidence.

There are four different materials considered. First the slab is removed and the antenna radiates in free space. Next a dielectric slab with relative mu = epsilon = 4 is considered. This slab has the same impedance as free space so should have no reflections at its interfaces.