Performance of the modified Berenger PML absorbing boundary condition for evanescent waves in three-dimensional structures

The recently proposed modified PML (MPML) absorbing boundary condition is extended to three dimensions. The performance of the MPML is investigated by implementing FDTD simulation of a typical microstrip line. The dominant mode and the first higher order mode of the microstrip line are excited separately. In both cases of excitation, the reflection properties of the MPML boundaries are examined, respectively. Numerical results reveal that by choosing appropriate values of the introduced permittivity and permeability, efficient absorption of both evanescent waves and propagating waves can be realized over a wide frequency band.