A special higher order finite-element method for scattering by deep cavities

A special higher order finite-element method is presented for the analysis of electromagnetic scattering from a large, deep, and arbitrarily shaped op en cavity, This method exploits the unique features of the finite-element e quations and, more importantly, the unique features of the problem of scatt ering by a large and deep cavity, It is designed in such a manner that it u ses minimal memory, which is proportional to the maximum cross section of t he cavity and independent of the depth of the cavity, and its computation t ime increases only linearly with the depth of the cavity, Furthermore, it c omputes the scattered fields for all angles of incidence without requiring significant additional time. The technique is inplemented with higher order tetrahedral and mixed-order prism elements, both having curved sides to al low for accurate modeling of arbitrary geometries. Numerical results show t hat higher order elements yield a remarkably more accurate and efficient so lution for scattering by three-dimensional (3-D) cavities. Of the two kinds of element, the mixed-order prism is optimal for the proposed special solv er.