Staircasing errors due to orthogonal meshing of electromagnetic cavities in FDTD

Staircasing of surfaces is a known and well documented source of error in FDTD models on orthogonal structured meshes; however, very little work focuses on such errors in simulations of electromagnetic cavities. This work examines the different errors that arise as a direct result of using an orthogonal approximation of a hollow spherical shell. The spherical shell used has a radius of 1 m and is constructed of a simple material with a conductivity σ = 1000 S/m and a thickness h = 1 mm. This material was represented using a thin boundary SIBC model allowing a mesh size much larger than the thickness of the material. The orthogonally meshed sphere was illuminated using a planewave and the electric field measured at the centre allowing the shielding effectiveness (SE) to be calculated.