On the use of local absorbing boundary conditions for RF scattering problems

Results are presented for combining the finite-element method with two types of absorbing boundary conditions (ABCs): the Engquist-Majda and the Bayliss-Turkel. The results are compared with closed-form solutions and with the results of hybrid techniques. Both absorbing boundary conditions are of the second order. All of the examples are for two-dimensional frequency-domain scattering problems. It is found that the Bayliss-Turkel ABC is more accurate than the Engquist-Majda type. Additionally, the Bayliss-Turkel ABC allows the exterior boundary to be brought closer to the object of interest, thereby reducing the number of unknowns and the computational effort. However, the Bayliss-Turkel ABCs become complicated if the exterior boundary is not circular