A COMPARATIVE-STUDY OF AN ABSORBING BOUNDARY-CONDITION AND AN ARTIFICIAL ABSORBER FOR TRUNCATING FINITE-ELEMENT MESHES

The type of mesh termination used in the context of finite element for mulations plays a major role on the efficiency and accuracy of the fie ld solution. In this work we evaluate the performance of an absorbing boundary condition and an artificial absorber (a new concept) for term inating the finite element mesh. This analysis is done in connection w ith the problem of scattering by a finite slot array in a thick ground plane. The two approximate mesh truncation schemes are compared with the exact finite element - boundary integral (FEM-BI) method in terms of accuracy and efficiency. It is demonstrated that both approximate t runcation schemes yield reasonably accurate results even when the mesh is extended only 0.3 wavelengths away from the array aperture. Howeve r, the artificial absorber termination method leads to a substantially more efficient solution. Moreover, it is shown that the FEM-BI method remains quite competitive with the FEM-artificial absorber method whe n the fast Fourier transform is used far computing the matrix-Vector p roducts in the iterative solution algorithm. These conclusions are ind eed surprising and of major importance in electromagnetic simulations based on the finite element method.