Balancing Boundary and Discretization Errors Using an Iterative Absorbing Boundary Condition

An iterative scheme is described for solving unbounded electromagnetic scattering problems using the finite-element method. The scheme starts with elements of a low polynomial order and progressively increases the order and improves the quality of the truncation boundary condition, so that the discretization error and boundary error are roughly similar at each stage. For the examples in this paper, errors in the radar cross section (RCS) are estimated. The discretization error estimate is obtained by the approximate solution of a problem in which all of the finite elements are one order higher. Results for a metallic cube, two dielectric spheres, a conducting ogive, and a conducting flat plate show that the scheme can obtain accurate bistatic RCS values very efficiently.