The Treatment of Singularities at 90 $^{\circ}$ and 270$^{\circ}$ Microstrip Corners in FDTD by the Modification of Assigned Material Parameters

It has been recently shown that the efficiency of the finite-difference time-domain (FDTD) method for structures containing thin wires and metal edges is much increased by using modified assigned material parameters (MAMPs). These parameters may be calculated empirically and in many cases analytically. In this contribution, the technique is extended to include the case of 90deg and 270deg corners in microstrip which may exist at an arbitrary position within the plane of the mesh. A semi-analytical method is presented and applied to the analysis of a complex patch antenna. Results are presented which show that the use of MAMPs allows a much larger cell size to be used than would be needed to achieve the same accuracy using standard FDTD.