Improved computational efficiency via near-field localization

The coefficient matrix which results when one applies the method of moments to the solution of the electric field integral equation is rendered sparse by appropriate selection of basis functions. These new basis functions arise when equivalent sources are arranged in such a manner as to produce a field focused on the bounding surface. The local nature of the focused fields reduces to a negligible level the interactions represented by many of the off-diagonal elements of the coefficients matrix. Moreover, the resulting basis appears to represent the surface fields more efficiently than many of the commonly used bases. The technique is currently limited to closed structures. Its application is demonstrated in two dimensions by computing the scattering of a plane wave by circular and square perfectly conducting cylinders. As the electrical size of the structure is increased and the number of unknowns is correspondingly increased, that the number of significant matrix elements per row is shown to remain approximately constant