Spherical Ports as a Direct Interface for Full-Interaction PO/MoM-to-FEM: Application to Lower-Frequency Satellite-Remote-Sensing Reflector-Based Antennas

This work presents a methodology for the direct combination of the field-based finite element method (FEM) with a current-based method, such as the method of moments (MoMs) or the physical optics (POs) method. The proposed methodology takes into account the multiple interactions between different parts (domains) where each one has been solved independently, retaining the full-wave nature, if present, of the independent methods used to solve each domain. It is based on the direct interconnection of: 1) a concave spherical port implemented on the current-based method (where a reflector or a scatterer is located) and 2) a convex spherical port defined over the FEM domain (where the feeder will be located). The methodology is first implemented in a proof-of-concept demonstrator, showing a very good correlation with a full-wave simulation of the complete structure for both return loss and radiated fields. Then, it has been successfully checked, in combination with the advantages inherited from the use of spherical ports (such as analytical replication, rotations, or translation) on a more realistic geometry: a satellite embarking a lower-frequency remote sensing instrument.