New representations for multipole moments and angular spectrum amplitudes of electromagnetic fields

Abstract

New results are reported, concerning the relationship between the multipole expansion and the angular spectrum plane-wave expansion of the electromagnetic field generated by a monochromatic localized charge-current distribution. An intimate connection between these two types of expansions is revealed. Based on these results, new source representations are obtained for the multipole moments and for the angular spectrum amplitudes. It is also shown how the field may be determined, at every point outside a sphere that contains the charge current distribution in its interior, from the knowledge of the radiation pattern.