Two-Step Method for the FDTD Analysis of Long Apertures Having Depth

In this letter, a two-step method has been proposed for the finite-difference time-domain (FDTD) analysis of long apertures having depth. The first step is to obtain the field distribution near the slot from a simple two-dimensional high-resolution FDTD simulation of the aperture areas, and then the field distribution is fully cast into the Yee cell to derive a slot integral coefficient. At the second step, the coefficient is applied to the cells containing the aperture with the contour path law to derive the slot updating equations. The validity of the proposed method has been approved from checking the accuracy of the field distribution of the first step and the slot coupling result. It is demonstrated the method presented here is stable and numerically and computationally efficient .