A current-based hybrid method for electromagnetic modelling of complex structures

This dissertation presents a general, unified hybrid method for radiation and scattering problems such as antennas mounted on a large platform. The method uses a coupled Electric Field Integral Equation (EFIE) and Magnetic Field Integral Equation (MFIE) formulation, referred to as the Hybrid EFIE-MFIE (HEM), in which the EFIE and MFIE are applied to geometrically distinct regions of an object. HEM is capable of modelling arbitrary three-dimensional metallic structures, including wires and both open and closed surfaces. It is shown that current-based hybrid techniques which utilize physical optics (PO) are an approximation of the HEM formulation.; A numerical solution procedure is given that combines the moment method (EFIE) with an iterative Neumann series technique (MFIE). This permits one to effectively utilize the PO approximation when appropriate, and provides a general and systematic mechanism to correct the errors introduced by PO. Consequently, HEM overcomes the inherent limitations of hybrid techniques which rely upon ansatz-based improvements of PO.; The method is applied to the problem of radiation from objects that can be modelled using wires and metallic surfaces as fundamental elements. A detailed development of the computer model is presented. In addition, an approximate method for handling dielectric sheets, known as Dielectric Physical Optics, is presented and a numerical study is given to demonstrate the accuracy of the method.; Finally, representative examples are given to demonstrate the accuracy of the calculations. Calculations for a satellite antenna are presented to demonstrate that the method can handle the difficult problem of a parasitic monopole located in the deep shadow region. In addition, calculations for a unique cavity-backed quad-slot antenna are given.