Assessment of spectral basis functions in BEM/FEM/GSM Domain Decomposition Methods for scattering and radiation applications

We have presented a sub-structuring domain decomposition method (DDM) devoted to electromagnetic computations, based on the boundary element method (BEM) and the finite element method (FEM). This computation procedure is applied to the analysis of antenna performance onboard vehicles. Spectral basis functions have been used and validated for expanding the electromagnetic fields on 3D interfaces separating the sub-domains. In this way, by masking the equipment on the large structure, our method enables us to greatly reduce the computation time of the large exterior domain with iterative solvers and MLFMA products. Thus, the SBF functions yield appreciable savings in computation time during the evaluation of the radiation of antennas mounted on large structures. In fact, the large exterior sub-domain is completely factorised and then computed once with BEM even in the case of parametric sweeps in the equipment sub-domains. At high frequencies, when the size of the structure supporting the equipment in term of wavelengths is prohibitive for BEM methods, hybridisation with asymptotic current techniques is carried out based on the reciprocity theorem. In this sub-domain method, the fact that the exterior unbounded domain becomes smooth enables us to consider the hybridisation with asymptotic geometric optic (GO) shooting and bouncing rays and physical optic (PO) currents methods. In this way, the feasibility of computing, with multidomain methodologies, the radiation patterns of complex antennas characterised by antenna manufacturers and mounted on a full scale motorglider, has been demonstrated.