Digital computer solutions of the rigorous equations for scattering problems

A survey of recently developed techniques for solving the rigorous equations that arise in scattering problems is presented. These methods generate a system of linear equations for the unknown current density by enforcing the boundary conditions at discrete points in the scattering body or on its surface. This approach shows promise of leading to a systematic solution for a dielectric or conducting body of arbitrary size and shape. The relative merits of the linear-equation solution and the variational solutions are discussed and numerical results, obtained by these two methods, are presented for straight wires of finite length. The computation effort required with the linear-equation solution can be reduced by expanding the current distribution in a series of modes of the proper type, by making a change of variables for integration, and by employing interpolation formulas. Solutions are readily obtained for a scattering body placed in an incident plane-wave field or in the near-zone of a source. Examples are included for both cases, using a straight wire of finite length as the scattering body. The application of these techniques to scattering by a dielectric body is illustrated with dielectric rods of finite length.