Large planar scatterers can be analyzed either by a direct moment method scheme, leading to block Toeplitz matrices for certain geometries, or via iterative techniques. In any case the physical optics component of the solution is readily known, hence the burden of its computation should be eliminated. An inherent separation between the physical optics and the remaining “fringe current” components is achieved by the use of the equivalent current representation of the incident fields. This representation has been beneficial in the recently introduced “add-on” scheme, as well as other methods based on modular computations. In this work it is used to provide an extra degree of efficiency to the analysis of electromagnetic scattering problems from planar structures with many incident fields. The approach extends the capability of a recently introduced method whereby a class of incident electric fields is represented by a set of basis functions. Here the equivalent incident current is expanded into a set of basis functions restricted to a limited aperture region only, facilitating the computation of the fringe current only. The response to any incident field is synthesized subsequently from the responses to these excitations. This results in a stable scheme which can efficiently treat large problems with many excitations.