A Domain Decomposition Method for the Analysis of Mutual Interactions Between Antenna and Arbitrary Scatterer Using Generalized Scattering Matrix and Translation Addition Theorem of SWFs

The effect of mutual coupling between an antenna and an arbitrary scatterer on both the reflection coefficient at the antenna input terminal and the total radiated field is investigated using a domain decomposition method (DDM). The electromagnetic fields are expanded in terms of spherical wave functions (SWFs) where the antenna and scatterer are characterized by their corresponding generalized scattering matrix (GSM) and transition matrix (T-matrix), respectively. The analysis involves scattering from the antenna structure, which makes it possible to take into account the higher order interactions. The mutual interactions between the antenna and the scatterer are considered using translation addition theorem for SWFs. Since the proposed method investigates the antenna and scatterer independently, their results may be stored to be reused if one or their relative position is changed. The numerical examples show an acceptable consistency between the results of the proposed method and those of commercial software simulations which can verify the proposed method. These examples show that in the presence of the scatterer, the scattering from the antenna structure has to be taken into account if one is interested in the total radiated field, whereas, for the evaluation of the antenna reflection coefficient, it may be neglected.