Optimal Edge Expansion Functions (EEF) Used in a Subsectional Expansion Scheme to Analyze Microstrip Antennas with the Method of Moments

The technique of solving integral equations, describing a microstrip antenna structure, with the method of moments is well known and widely used. In this paper an efficient procedure is given to determine subsectional edge expansion functions containing the correct singularities of the currents at the edges (both the current parallel with and the current normal to the edge). It is proven that the use of these subsectional edge expansion functions considerably improves the convergence of the calculated resonant frequency.