Higher order mechanisms and couplings in the hybrid/sup 2/ method for calculating near and far fields of complex composite radiating structures

The hybrid method combining the finite clement method (FEM) and the boundary element method (BEM) is capable of solving antenna and scattering problems, which involve arbitrarily shaped and highly inhomogeneous objects. The addition of a third method, in this case the uniform geometrical theory of diffraction (UTD), leads to a new method with a double hybridization (hybrid/sup 2/ method) with extended capabilities for the efficient solution of more complex problems comprising arbitrarily shaped, highly inhomogeneous and electrically large objects. In this paper we investigate the behaviour of the hybrid/sup 2/ method, when it is applied to the calculation of the near and far fields of antennas located in the close vicinity of highly inhomogeneous and electrically large objects. For the case of several electrically large objects (called UTD-bodies) located close to each other, we show the necessity to account for higher order mechanisms e.g. diffraction followed by reflection. We also focus on the influence of those large objects on the current distributions of the FE-BE bodies (e.g. antennas) due to the strong coupling between them. The strong interactions between the antenna and its close environment can change the original far-field characteristics of the antenna considerably. The changed radiation diagram of the antenna can then be used for further investigations, for example for path predictions in mobile cellular systems.