Finite-element based iterative hybrid techniques for the solution of electrically large radiation problems

Most of hybrid techniques developed so far are mainly based on the method of moments (MOM) with high-frequency asymptotic techniques (HFATs). As a result, this type of hybrid methods is not suitable when the source region contains material inhomogeneities and anisotropies. The finite element method (FEM) is proven to be the most appropriate method to treat material and geometrical complexities. Here, the FEM is hybridised with HFATs to analyze antennas mounted on or placed near a large complex structure. The antenna itself and its vicinity belong to the low-frequency regime; therefore, it will be treated by a low-frequency method such as the FEM. Whereas, the large scatterer belongs to the high-frequency regime and is well suited to HFATs such as physical optics (PO) and/or geometrical theory of diffraction (GTD). Both solutions are combined to produce the total fields in such a manner that the FEM and HFATs computations are performed separately, yet the presence of the other domain is fully taken into account through an iteration algorithm. A representative example is given to demonstrate that the method can successfully reconstruct most of the interactions occurring between the low- and high-frequency domains. Consequently, the accuracy of the hybrid method is shown to be almost the same as that of a full-wave analysis provided all possible interactions and their higher-order terms are fully taken into account.