Accurate modeling of field singularities at metal edges diagonal to the FD-TD grid

Using the knowledge of quasi-static electromagnetic fields near a sharp metal edge, new FD-TD update equations are derived for nodes close to an edge that runs diagonally across the faces of cubic Yee cells. With this enhancement to the standard FD-TD method, the field singularities at the metal edge can be properly modeled using a coarse mesh. An analysis of a homogeneous strip line shows that the new field-enhanced FD-TD equations dramatically improve the accuracy of the computed effective dielectric constant, when compared with the shape-enhanced (conformal) FD-TD equations and the staircase approximation. There is no noticeable increase in the computing time or memory.