STABILITY OF THE FDTD ALGORITHM ON NONORTHOGONAL GRIDS RELATED TO THESPATIAL INTERPOLATION SCHEME

In this paper we present a reformulation of the FDTD algorithm on nono rthogonal grids, which was originally proposed by Holland in 1983. Bas ed on the matrix-vector notation of the Finite Integration Technique ( FIT), the new formulation allows to study a special type of instabilit y, which is due to the spatial discretization and independent of the c hoice of the timestep. It is shown, that this type of instability can be avoided by a symmetric evaluation of the metric coefficients of the nonorthogonal grid. Two numerical examples demonstrate the stability properties and the high accuracy of the new method.