A new absorbing boundary condition structure for waveguide analysis

Abstract

This paper presents a novel absorbing boundary condition structure for waveguide analysis, which attenuates evanescent waves and waves near cutoff frequencies. The existence of these waves limits the accuracy of the fields computed using tlic 1~I)'Tl) method, and prompted several rescarrhers to design complicated boundary conditions, including ronibinations of Phl I, and lligdon's higher-ordrr ABCs. Instcad, we employ a parallel plate terminating structure in which the lateral walls are made absorbing in addition to the longitudinal walls. The iindcsirable lateral waves at the normal boundary intcrfacr, a dominant soiirce of error, are slowed down and cffectively attenuated in the lateral walls, while the propagating waves are absorbed in the longitudinal walls. No lossy materials are employed for absorption.