Characteristic modes and dipole representations of small apertures

Abstract

In this paper, characteristic modes of the magnetic current are related to the dipole representation of a small aperture in a conducting plane of infinite extent. Low‐frequency approximations are used to simplify the eigenequations for the first three characteristic currents. It is shown that these three characteristic currents are closely related to the three dipoles of Bethe hole theory. An example of a small circular aperture in an infinite conducting plane is discussed.