An engineer's approach for terminating finite element meshes in scattering analysis

When solving open-region scattering problems via the finite-element method, the infinite region exterior to the scatterer must be truncated with an artificial boundary in order to limit the number of unknowns. An approach that can be used to truncate the infinite region in a finite-element analysis is proposed which involves an artificial conducting boundary (either electric or magnetic). As can be expected, this boundary will cause nonphysical reflections of the scattered field; however, these can be minimized by coating the inner face of the boundary with a layer or several layers of fictitious dielectric whose thickness and constitutive parameters can be so chosen that it absorbs the field over a wide range of incidence angles. Based on the formulation presented, a simple finite-element program was written using a banded matrix algorithm with a variable bandwidth storage scheme. Numerical results are presented.<>