Field expansions in terms of conical and localized beams

This paper compares some methods for computing aperture radiated fields by means of localized beams and conical (non localized) beams. It is seen that all types of beams can be generated in a simple way starting from the spectral-domain radiation integral, by expanding the aperture electric field spectrum in a sum of complex exponentials using the Generalised Pencil-of-Function (GPOF) method [1]. This operation transforms the radiation integral into a simpler form, which can be evaluated analytically. Two different beam expansions are thus derived, both of them arising from the same spectral GPOF process, which possess different properties with respect to the number of beams required to get a certain accuracy.