Inverse source characterization for electromagnetic near field reconstruction and interaction with the environment

Antennas are sources of electromagnetic radiation. The radiation pattern and gain can be routinely obtained by measurements and characterize efficiently the radiation of the source regardless of its actual complexity. However in some applications, one may need to analyze the source interaction with its close environment in the near field region instead of the far field one. In this paper, we partition the antenna geometry with overlapping smaller spheres than the minimum one. The field at a point in the near field is the superposition of the field radiated by the sub-sources or equivalent sources circumscribed by the small spheres. The inverse or synthesis problem is to find these equivalent sources given the radiation pattern or its spherical harmonics spectrum. The radiated fields of the equivalent sources are expanded in terms of spherical harmonics which is locally associated with their minimum spheres