An asymptotic evaluation of a kernel in the study of a radiation operator: the strip current in near zone

In this paper we consider a radiation operator T in near non reactive zone, and we study the analytical properties of the operator TT* In particular, first we perform an asymptotic evaluation of the kernel of TT*; later, we derive a closed-form approximation of the eigenfunctions of such a operator which is valid on a subset of the observation domain. The study is done with reference to a magnetic strip current whose radiated electric field is observed on a bounded observation domain parallel to the source