“…Generally speaking, it is known that in FDFD (and FDFD) methods the assignment of the material properties to the grid cells (e.g., µ i,j,k r,xx ) is a fundamental step which can be performed by various techniques [29,33,34]. In [26], the pointwise value of the constitutive parameters has been assigned to each node in the Yee grid (i.e., µ i,j,k r,xx = µ r,xx (i∆x, (j + 0.5)∆y, (k + 0.5)∆z), for example), and the discretization grid has been chosen in order to avoid that any node could lay on a discontinuity of the dielectric permittivity or of the magnetic permeability [26].…”