Resonant behavior of a small aperture backed by a conducting body

The problem of an electrically small aperture in a conducting screen backed by a conducting body is analyzed. It is found that aperture-body resonances can occur for which the power transmitted through the aperture backed by a conducting body is much larger than that when the body is not present. An example is an electrically small aperture resonated by a capacitor across its midpoint. In the loss-free case, the transmission cross section of a small resonated aperture is independent of the size or shape of the aperture. For actual conductors, the transmission cross section will be increasingly reduced by conduction loss as the aperture is made smaller.