Plane wave transmission through a pair of capacitive gratings

A frequency-selective structure is investigated that represents a pair of gratings with narrow gaps in a thin conductive screen separated by a dielectric slab. In particular, the gratings may be closely spaced. The calculations show that the parasitic windows of the transparency may be shifted far from the operational frequency to the high frequency region, so that the ratio of the frequencies of the parasitic and operational windows of the transparency will exceed four. Expressions for the reflection and transmission coefficients are obtained. The results of calculations are compared with experimental data in the cases of both normal and oblique incidence.