On the spatial structure of the antenna electromagnetic near field

This paper presents a general theory of the antenna near field in the spatial domain. The approach is based on using the Wilcox expansion of the radiated field to define a set of asymptotic spherical regions covering the entire exterior space of the antenna problem. Careful examination of the energy expression within this picture revealed the rich and complex interaction mechanisms between the various spherical regions indicated above. The multipole expansion is then utilized to construct nonrecursively the full near field in the exterior region starting from the far field only. The analysis led to interesting theorems regrading energy exchange processes in the near zone and also to a completely analytical evaluation of the antenna reactive energy in terms of the TE and TM modes of the antenna system.