Cylindrical FDTD with improved time step size based on hybrid Newmark-Beta discretization

A hybrid FDTD update scheme for cylindrical meshes is proposed in order to overcome limitations on the maximum stable time step that arise from inherently small grid steps. The algorithm combines the advantages of explicit central differencing schemes and implicit, but therefore unconditionally stable, Newmark-Beta schemes. It is shown to yield the same results as an existing algorithm for this purpose, but in a more intuitive fashion. Furthermore, a modification for rotationally symmetric structures is introduced and used in a numerical example.