Multigrid TLM for diffusion problems

The multigrid technique, which is mainly used in the finite difference method, is applied to the TLM (transmission‐line matrix or modeling) procedure. In the multigrid TLM, the field region is covered with sets of regular transmission‐line matrices of different mesh sizes. The finer grid pattern, which overlaps the coarser grid, fills the region with high field gradients. Data obtained in the coarser grid are transferred to the finer grid through an interpolation process and used as boundary conditions for the latter. The finer grid data are then transferred back to the coarser one, thus improving the coarse grid values. The method is applied to several diffusion problems and significant improvements in accuracy and efficiency are shown.