Evaluation of a thin-slot formalism for finite-difference time-domain electromagnetics codes

A thin-slot formalism proposed by Gilbert and Holland (1981) for use with finite-difference time-domain (FDTD) electromagnetics codes has been evaluated in both two and three dimensions. This formalism allows narrow slots to be modeled in the wall of a scatterer without reducing the spatial grid size to the slot width. In two dimensions, the evaluation involves the calculation of the total fields near two infinitesimally thin coplanar strips separated by a gap. A method-of-moments (MoM) solution of the same problem serves as a benchmark for comparison. Results in two dimensions show that up to 10 percent error can be expected in total electric and magnetic fields both near (λ/40) and far (1 λ) from the gap. In three dimensions, the evaluation is similar. The finite-length slot is placed in a finite plate and an MoM surface patch solution is used for the benchmark. These data show that slightly larger errors can be expected