Mutual Coupling Analysis of Arrays of Antennas with Overlapping Minimum Spheres Based Exclusively on Addition Theorems

Mutual coupling in antenna arrays is calculated in the case of elements with overlapping minimum spheres. Taking the Generalized Scattering Matrix of an isolated element as the starting point, mutual coupling is calculated exclusively through the application of addition theorems for spherical vector waves. To this aim, the addition theorems are used not only to relate the scattered field of one element in the array to the incident field on another one, as usual, but also to change the coordinate origin of the incident or scattered field. This approach is compared with that based on the transformation between spherical and plane vector waves, showing similar precision.