On matching of equivalent field regions: the aperture problem revisited

In aperture problems equivalent magnetic currents in the aperture region are employed for each region by invoking the equivalence principle and by enforcing the boundary condition for the tangential components of the electric field. Subsequently an integral equation is formulated by satisfying the boundary condition for the tangential component of the magnetic field in the aperture region. In the case of an aperture in a perfectly conducting screen with impressed source currents assumed on the one side, we discuss an alternative procedure. This procedure makes use of the fact that in the aperture the tangential component of the magnetic field due to the induced currents in the screen is zero. The use of such a procedure demonstrates the continuity of fields across the aperture. The purpose of this tutorial paper is to compare the new procedure and the conventional procedure and to provide additional insight into the field components, both tangential and normal.