Enhanced FD-TD equations for sharp, diagonal, metal edges at arbitrary angles

Considering the singular nature of electromagnetic fields at a sharp metal edge, new FD-TD equations are derived for critical electric and magnetic nodes near such edge, which is diagonal along the Yee-cell faces in a general (not necessarily cubical) FD-TD grid. With these enhanced equations, a metal edge at an arbitrary angle to the grid can be modelled very accurately using a course grid. Analysis of several microstrip and strip lines shows that the new equations are very stable, and the computed effective dielectric constant is significantly more accurate than with previous techniques. There is no noticeable computing overhead (time or memory) of the new technique. The new equations, which differ from standard FD-TD equations only by a few additional coefficients, can be easily implemented in a standard FD-TD code.