TLM Modelling of Electromagnetic Structures Using Static Sub-Griddings

In transmission line matrix modelling the space discretization of the electromagnetic structures is related to the wavelength. Usually it is assumed that the spatial discretization interval should not be larger than 5 percent of the shortest wavelength occurring in the signal spectrum. However, if the electromagnetic structure exhibits fine details, strong field variations may occur within much smaller spatial distances. However, within this short distances the field variations are determined by the electrostatic and magnetostatic field solutions. Therefore the computational effort may be reduced considerably by introducing a static sub-gridding. In this case, with the static sub-grid, the electrostatic and magnetostatic field solutions are computed and are used to compute correction factors for the larger cells used in the TLM electrodynamic simulation. The method is applied to a MS-stub on a Silicon on Insulator wafer in the frequency range of 90 to 140 GHz. Simulation results are compared with measurements.