  Using a dipole interaction model, we derive generalized sheet transition
conditions (GSTCs) for electromagnetic fields at the surface of a metascreen
consisting of an array of arbitrarily shaped apertures in a perfectly
conducting screen of zero thickness. Use of the GSTCs permits modeling of
structures containing perforated surfaces much more rapidly than is possible
with full-wave numerical simulations. These conditions require that the period
of the array be smaller than about a third of a wavelength in the surrounding
media, and generalize many results previously presented in the literature. They
are validated by comparison with results of finite-element modeling, and show
excellent agreement when conditions of their derivation are satisfied.
