Computer-aided design-based high-frequency electromagnetic wave scattering from complex bodies

This work investigates the use of high frequency electromagnetic scattering techniques, such as the physical theory of diffraction (PTD) and the geometrical theory of diffraction (GTD) and the shooting and bouncing rays (SBR) method combined with computer aided design (CAD) compatible geometries, to perform the electromagnetic scattering analysis of complex arbitrary bodies. The use of CAD formats such as solid modelled bodies and bodies modelled with triangular patch surface elements allows the scattering analysis of arbitrary bodies which can be constructed using CAD packages. The scattering analyses are applied to radar cross section (RCS) problems, cavity radiation problems, and antenna pattern predictions of complex electrically large structures, thereby showing that it is feasible to accurately approximate the electromagnetic wave scattering from general complex bodies using CAD techniques and high frequency scattering techniques.;First the RCS of large targets which involve multiple geometric optics (GO) interactions are investigated by comparing the RCS calculated using CAD designed radar targets and the SBR method and PTD for targets such as trihedral corner reflectors and an idealized military vehicle model with the experimentally obtained RCS. The comparisons between the calculated and measured results demonstrate that the SBR and PTD can provide accurate approximations of the RCS for targets which have complex multiple GO interactions.;Second, the problem of interior cavity radiation for closed cavities is approached using a ray tracing and GO method based on the SBR method and triangular surface patch described geometies. Comparisons between the ray-based calculations and more exact techniques such as the method of moments (MM) for two-dimensional cavities demonstrate that ray-based methods can provide good approximations for the field behavior inside of nonresonant cavities. A three-dimensional case is shown to demonstrate that this technique can be easily applied to three-dimensional problems.;Third, the GTD is applied to the problem of three-dimensional electromagnetic wave propagation in complex environments. These environments are described using triangular patch surface models compatible with CAD packages. This technique is applied to two different types of propagation problems: antenna pattern prediction in complex realistic environments and long distance radio wave propagation. Comparisons between theoretical GTD results and those for experimental and other theoretical methods demonstrate that using GTD and CAD based models, the electromagnetic wave propagation can be accurately predicted for complex problems.