The dyadic Green's function for an electric current source placed in a rectangular waveguide is derived using a magnetic vector potential approach. A complete solution for the electric and magnetic fields including the source location is obtained by simple differentiation of the vector potential around the source location. The simple differentiation approach which gives electric and magnetic fields identical to an earlier derivation is overlooked by the earlier workers in the derivation of the dyadic Green's function particularly around the source location. Numerical results obtained using the Green's function approach are compared with the results obtained using the Finite Element Method (FEM). Deshpande, M. D. Langley Research Center NAS1-19341; RTOP 522-33-11-02

This book deals with the design and analysis of fractal apertures in waveguides, conducting screens and cavities using numerical electromagnetics and field-solvers. The aim is to obtain design solutions with improved accuracy for a wide range of applications. To achieve this goal, a few diverse problems are considered. The book is organized with adequate space dedicated for the design and analysis of fractal apertures in waveguides, conducting screens and cavities, microwave/millimeter wave applications followed by detailed case-study problems to infuse better insight and understanding of the subject. Finally, summaries and suggestions are given for future work. Fractal geometries were widely used in electromagnetics, specifically for antennas and frequency selective surfaces (FSS). The self-similarity of fractal geometry gives rise to a multiband response, whereas the space-filling nature of the fractal geometries makes it an efficient element in antenna and FSS unit cell miniaturization. Until now, no efforts were made to study the behavior of these fractal geometries for aperture coupling problems. The aperture coupling problem is an important boundary value problem in electromagnetics and used in waveguide filters and power dividers, slotted ground planes, frequency selective surfaces and metamaterials. The present book is intended to initiate a study of the characteristics of fractal apertures in waveguides, conducting screens and cavities. To perform a unified analysis of these entirely dissimilar problems, the “generalized network formulation of the aperture problems” by Mautz and Harrington was extended to multiple-aperture geometry. The authors consider the problem of coupling between two arbitrary regions coupled together via multiple apertures of arbitrary shape. MATLAB codes were developed for the problems and validated with the results available in the literature as well as through simulations on ANSOFT's HFSS.

First produced by the Swedish Association of Metalworking Industries.

Three systems of waveguide discontinuities are considered. The first system is that of multiple apertures of arbitrary shape in the transverse plane between two cylindrical waveguides. The second system consists of metallic obstacles in a rectangular waveguide that are uniform along the narrow side of waveguide but are otherwise of arbitrary shape and thickness, i.e., a system of inductive posts. The third system consists of metallic obstacles in a rectangular waveguide that are uniform along the broad side of the waveguide, but are otherwise of arbitrary cross section and thickness, i.e., a system of capacitive posts. Common between the first and second systems are the inductive windows and strips in a rectangular waveguide, and between the first and third systems are the capacitive windows and strips in a rectangular waveguide.