Recently an unconditionally stable ADI method was successfully applied to the solution of Maxwells equations using a variation of the FDTD method [1, 2]. The ADI method is most useful for solving problems where the lattice is grossly over discretized spatially (< 1O{sup}-2 λ{sub}min). For this scheme to be applicable to analyzing practical electromagnetic interaction problems, an efficient absorbing boundary condition that maintains unconditional stability must be derived. In thin paper, an absorbing boundary condition using a perfectly matched layer (PML) is introduced. Specifically, the convolutional PML (CPML) method [3] is used with complex frequency shifted scaling coefficients [4]. It is shown that this method maintains unconditional stability. Further, it is demonstrated that the method provides a significant improvement in the reflection error as compared to the originally proposed split-field PML ADI scheme [5].
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