Efficient description of fine features using digital filters in time-domain computational electromagnetics

The use of digital filters for the description of perforated metal plates in the time-domain transmission-line modelling (TLM) method is presented. The frequency-domain Prony method is used to approximate the analytic scattering coefficients of perforated plates using Laplace-domain functions. These functions are transformed into the T-domain and the resulting digital filters are embedded into the TLM mesh. Three types of perforated plates are studied and the results obtained for the shielding effectiveness of equipment enclosures having perforated plates are shown.