Fast finite-difference time-domain (FDTD) method of two dimensional target scattering calculation by two-level hierarchical approach

Abstract

This paper presents a fast finite-difference time-domain (FDTD) method to calculate the scattering of heterogeneous target by utilizing effective electrical properties of the material in local areas. The heterogeneous target sometimes can be a really large model, which may be time-consuming and requires significant computer resources to finish the scattering computation using FDTD method. For complex target, the grid must be very small to fit the detail of the material's distribution. To overcome this issue, we propose a two-level hierarchical approach to reduce the grid number of the model in scattering calculation. In level one, the model is partitioned to many small grids to fit the target's heterogeneous characteristics. Each grid is assigned a value of electrical property at that position. In level two, the model is then partitioned to big grids, each of which covers several small grids. The electrical property in each big grid is treated as homogeneous and the electrical value is obtained with the values of the small grids within it. These big grids are then applied in FDTD method to calculate the scattering of the target. Finite-difference method (FDM) and Bruggeman formula are utilized to calculate the effective property in each big grid. FDM can give the anisotropic properties of the material, while Bruggeman formula can only yield isotropic ones. Numerical experiment of a human head slice is conducted and the results show the accuracy and efficiency of the two-level hierarchical method.