The use of subgrids in the finite-difference time-domain method to facilitate the analysis of multiscale problems is now well established. However, many of the proposed algorithms are restricted to cases where the subgrid and the main grid share the same Cartesian coordinate system and where the ratio of the cell sizes in the two grids has a constant integer ratio. More recently, it has been shown that subgrids, based on Cartesian grids which are rotated with respect to the main grid, can be effectively used, but the cell size ratio was still kept constant. In this contribution, the method is further generalized in order to allow nonuniform subgrids to be used. This greatly increases the range of structures which can be efficiently analyzed. The effectiveness of the method is demonstrated by application to a 31-element hemispherical array of broadband cavity backed slot antenna elements.
- Finite-difference time-domain (FDTD) methods