An improved accuracy version of the method of auxiliary sources for computational electromagnetics

The method of auxiliary sources (MAS) is normally applicable to electromagnetic problems involving structures of significant thickness, so that an adequately large distance between source and collocation points is guaranteed. For thin or open geometries the accuracy of the method is depleted, due to numerical instabilities caused by the highly singular terms of the dyadic Green´s function (DGF). In this paper a modified MAS (MMAS) is developed to circumvent this particular difficulty. Higher order terms of the DGF are numerically calculated by introducing a canonical grid, where derivatives can be accurately computed via a discrete scheme, unlike standard MAS, where the DGF analytical, problematic expression is invoked instead. This procedure is equivalent to the involvement of auxiliary currents and charges in the solution, instead of the elementary source fields used in standard MAS.