A "subtract-off" formulation for large finite conducting surfaces

The add-on scheme is extended to include the aperture formulation. Rather than adding elementary conductors along the fixed coordinate surface, one now adds elementary apertures, which are being gradually cut, or subtracted off, from the original conductor. The adaptation of the add-on scheme to the aperture formulation involves the replacement of the electric current by the electric field as the basic quantity. Duality shows that the properties of the patch formulation are retained in the aperture formulation. For example, in the patch formulation, efficiency also benefits from the fact that only sources located on the aperture require computation. In accordance with duality, only sources located over the conductor require computation in the aperture formulation.<>