Scattering analysis of large-scale cavities using the nonstandard FDTD method

The nonstandard FDTD method has been proposed for highly accurate numerical analysis of large structures. However, the conventional nonstandard FDTD h as been defined only with isotropic grids, and hence the treatment of arbit rary cavity shapes has been severely restricted. In order to remove this re striction in this paper, the nonstandard FDTD method is extended to more ge neral nonisotropic grids. First, the FD Laplacian for the nonisotropic grid s is newly defined. From the expression for decomposition by the first-orde r difference operator, the nonstandard FDTD equations are derived for nonis otropic grids. The physical meaning of the nonstandard FD method used in th e nonstandard FDTD method is clarified. Next, by means of the nonstandard F DTD method extended to nonisotropic grids, a scattering analysis of large-s cale cavities is performed and its effectiveness is demonstrated. The resul ts obtained by the nonstandard FDTD method agree well with the measured val ues, confirming that the nonstandard FDTD method is effective as a highly a ccurate scattering analysis method for large-scale cavities. (C) 2001 Scrip ta Technica.