Characteristic modes for a slot in a conducting plane, TM case

Consider an infinitely long slot in a conducting plane in an unbounded medium illuminated by a uniform transverse magnetic (TM) (to the slot axis) plane wave. The theory of characteristic modes for apertures is applied to solve the problem. For a narrow slot, analytic expressions for the first two characteristic currents and the equivalent magnetic current are given. As computed by the method of moments, numerical results for the characteristic currents and fields, the equivalent magnetic current, and the transmitted field pattern are presented for the slot whose width is one wavelength.