Enhanced FD-TD equations for diagonal metal edges and their microwave applications

The standard FD-TD method requires a very fine grid to model singular fields in the vicinity of sharp metal edges. This is a problem for simulating microwave structures composed of thin metal sheets, such as planar transmission lines and patch antennas. We have derived improved (enhanced) FD-TD equations for diagonal metal edges by considering field singularity. With these equations, various microwave structures can be analyzed accurately using a much coarser grid. In this paper, we demonstrate the application of enhanced FD-TD equations in: (1) modeling wave propagation in diagonal microstrip lines; and (2) simulating resonance in microstrip patch antennas. The accuracy of numerical results was improved by a factor of between 4 to 10, without additional computational overhead (time or memory).