Electromagnetic scattering from a two-layered frequency selective surface of finite width

One of the major difficulties in analyzing a finite FSS (frequency-selective surface) is the need to handle large matrices, since the current distribution of each individual patch must be treated as a separate unknown quantity. This problem is exacerbated by the introduction of additional layers that are commonly used in many practical designs. However, for a two-layer FSS, where the two layers are identical and symmetrically disposed about the z=0 plane, the solution can be constructed by solving the single-layered problem twice: once with a perfectly electric conducting (PEC) and the second time with a perfectly magnetic conducting (PMC) wall inserted at the plane of symmetry. This approach is used to calculate the plane-wave scattering by a two-layered FSS that is truncated along the horizontal direction, and is embedded in a dielectric layer. The unit cell of the FSS is a cross-dipole. The results for a TM-polarized incident field exhibit a great deal of difference between the pattern characteristics of the single and double-layered FSS. For instance, while the pattern for the single-layered case shows the expected symmetry, it is highly asymmetric for the two-layered case, with only a small portion being scattered in the lower hemisphere, i.e. in the forward direction.<>