Numerical methods for current analysis in microstrip planar antennas

Attention is called to the limitations of the methods that have been proposed for determining the current distribution of the upper conductor, noting that the methods neglect either the open or the inhomogeneous characteristics of microstrip antennas. What is more, the existing surface wave is never taken into account. It is noted that the exact integral equation recently developed by Rana and Alexopoulos (1979) for printed wire antennas can be generalized to planar microstrip antennas. This entails taking for its kernel the dyadic Green's function giving the tangential electric field created by a horizontal Hertz dipole placed on the antenna's surface. The numerical methods for evaluating this kernel, together with certain aspects of a moment method solution, are discussed.