Subwavelength structures (SWS) are periodic diffraction structures. A plane wave with
wavelength less than the periodicity produces a zeroth order reflection.

Unlike planar FSS structures, subwavelength structures are three dimensional in
nature.

The usual method for computer modeling them is to use rigorous coupledwave theory
(R.C.W.T.). This method provides excellent agreement with measured results.

R.C.W.T. considers structures as a dielectric material, however, metals can be modeled
by using a complex permittivity to approximate the metal's conductivity.

The drawback to modeling metals with this method is that it requires a large number of
waves to be used in the calculation (resulting in extended computation time).
