Scattering by spherically stratified microwave lens antennas

A comprehensive treatment of scattering by sources in the region of a spherically stratified object composed of discrete shells is presented and compared with measured results. The work encompasses the developments necessary for a thorough understanding of the focusing mechanism of a spherical lens. The method used is a modal technique that employs separation of variables in order to determine an eigenfunction representation of the incident and scattered fields. This formulation provides the Green's function required for the calculation of the scattering from a multiple layered sphere excited by an infinitesimal current element. The algorithm allows both near- and far-field predictions. The scattering by more complicated source field distributions is modeled by applying superposition with the appropriate coordinate transformations. From a practical standpoint, the present analysis allows the limitations of spherical lenses to be determined while providing the information required to optimize the lens design. A system was built based on the new design data, and its measured radiation characteristics are compared to the theoretical predictions. Excellent agreement is observed in most cases