Combined spatial and spectral techniques for the analysis of microstrip antennas

In this paper techniques are presented, that permit an efficient full-wave analysis of printed structures with metalization of arbitrary shape, based on the electric field integral equation (EFIE) formulation and discretization by application of Method of Moments (MoM). For the analysis of a single element, the leading, frequency independent singular terms of the Green function are extracted and the part of impedance matrix associated to them is evaluated in space domain. The eigenfunctions of these terms are then used for expanding the regular part; they are entire-domain functions, defined for an arbitrary geometry, and incorporate the correct edge behavior: therefore only a reduced number of them is necessary to well represent the solution. For the application to arrays, the effort needed for the evaluation of the coupling integrals between two arbitrary functions on separated domains is reduced via a spectral domain formulation, with numerical integration along a path of rapid convergence. Application examples and validations are presented.