Improved impedance boundary condition for finite elements by cross-coupling at corners

Within a conductor the field near a corner is represented by two modes, each of which is a solution of the diffusion equation. The resulting relationships between normal and tangential fields on the conductor surface are thereby extended from right-angled corners discussed previously to those of any angle, and are shown to reduce to the well-known surface impedance expression as a plane surface is approached, These surface expressions are implemented by cross-coupling scalar potential values across the corner in a 2-D finite-element computation and are compared with a vector potential computation which includes the conductor