Electromagnetic scattering by an aggregate of spheres: Theoretical and experimental study of the amplitude scattering matrix

An accurate analytical representation of the amplitude scattering matrix is of key importance in the development of a reliable electromagnetic scattering formulation, because it enables one to derive rigorous analytical expressions for all scattering quantities. We compare a rigorous theory of scattering by aggregates of spheres [Y.-I. Xu, Appl. Opt. 36, 9496 (1997)] with a large set of laboratory microwave analog scattering measurements for multiple spheres obtained by Wang between 1968 and 1983. Close agreement is found for all of the experimental data tested, confirming that the four amplitude scattering matrix elements can be accurately evaluated by the theory that is based on a far-field solution. It also leads to the validation of a simplified noninteracting-scattering (MS) approximation derived from the theory.