Analysis of Waveguides Filled with Uniaxial Media and Metamaterials for Filter Applications using the Mode Matching Method

This dissertation will explore the analysis of waveguide discontinuities for the purpose of dielectric filled waveguide filter analysis and design. The filling media studied are uniaxial media and uniaxial media embedded with metamaterial. A literary search provides numerous methods and numerical techniques for analyzing waveguide class problems, but ultimately the Mode Matching Method (MMM) is chosen as the numerical analysis technique for this dissertation. An overview of waveguide theory and its application to the Mode Matching Method are presented. The Mode Matching Method is then used to analyze simple cases to confirm the numerical accuracy. Once accuracy is confirmed, Mode Matching theory is applied assuming the waveguides are filled with anisotropic medium. This theory is extended to uniaxial media with special orientations of the optic axis, because in practice the coordinate systems of media and waveguide do not always coincide. The Mode Matching Method with rotated optic axis is also extended to include the losses of the dielectric. This thesis also goes on to demonstrate the Mode Matching Method can accurately analyze dielectric waveguides with embedded metamaterial, specifically thin wire metamaterials Finally two dielectric filled waveguide filters are designed using the Mode Matching Method: one filter with embedded metamaterials and one filter without metamaterials. The filters are then manufactured. The measured results are compared to the Mode Matching results and shown to have excellent agreement

Monolithic microwave integrated circuit devices for active array antennas

Two different aspects of active antenna array design were investigated. The transition between monolithic microwave integrated circuits and rectangular waveguides was studied along with crosstalk in multiconductor transmission lines. The boundary value problem associated with a discontinuity in a microstrip line is formulated. This entailed, as a first step, the derivation of the propagating as well as evanescent modes of a microstrip line. The solution is derived to a simple discontinuity problem: change in width of the center strip. As for the multiconductor transmission line problem. A computer algorithm was developed for computing the crosstalk noise from the signal to the sense lines. The computation is based on the assumption that these lines are terminated in passive loads

On the analysis of capacitive rectangular waveguide discontinuities close to arbitrarily shaped conducting and dielectric posts

In this work, we propose an integral equation technique for the efficient analysis of capacitive step discontinuities in rectangular waveguides. The method allows for the inclusion of a number of arbitrarily shaped posts in the vicinity of the step discontinuity. The posts can be both metallic or composed of homogeneous dielectric materials. The integral equation formulation is based on the Surface Equivalence Principle, and uses the parallel plate Green’s functions that take into account for the boundary conditions imposed by the host waveguide. The formulation is written in the mixed spatial-spectral frequency domain, and takes advantage of the symmetry of the problem by reducing the original three dimensional (3D) problem to a so called 2.5D problem. The numerical technique has been validated with simulation examples, namely, two lowpass filters that use conducting and dielectric posts of different shapes as impedance inverters. The results provided by the method that we propose have been also compared to those obtained with a commercial full-wave software tool (ANSYS HFSS), showing in all cases a very good agreement with substantially higher computational efficiency.This research work has been financially supported by the Spanish Ministerio de Economía y Competitividad in the frame of the projects Ref. TEC2016-75934-C4-1-R, and Ref. TEC2016-75934-C4-4-R. We also thank the Ph.D.scholarship granted by the Spanish Ministerio de Educación, Cultura y Deporte, with Ref. FPU15/02883

Passive Waveguide Components for Integrated Optics

This thesis incorporates studies of optical waveguiding in both planar and two dimensional (quasi-rectangular) waveguides of thin film Corning type 7059 glass. Single mode propagation in trapezoidal waveguide devices has been achieved throughout this investigation

Investigation of open periodic structures of circular cross section and their transition to solid circular waveguide

Previous work has already modelled an open periodic cylindrical tube constructed from a Frequency-Selective Surface (FSS) to form the Frequency-Selective Guide (FSG). This model is used to expand the understanding of the FSG and known mode content that it can support. The results of the model have been authenticated directly by measurement techniques. The range of FSGs measurements undertaken was expanded to enable greater understanding of the structure utilising parameters that could not be included in the theoretical model. This extensive measurement set combines with the modelled data to provide a very comprehensive understanding of the FSG operation based on both physical and theoretical data. [Continues.

Contribution to the characterization of stratified structures : electromagnetic analysis of a coaxial cell and a microstrip line

The objective of this dissertation is the development of electromagnetic modelling software specific to the cells of microwave material characterization. This development is based on numerical methods that are alternative to finite element method which is widely used in commercial software. For the need to extract the properties of materials by inverse modelling methods, research into the numerical efficiency of direct analysis is the focus in this thesis. The characterization targeted cells in this work concern a coaxial cell and a planar line. The presence of an unknown material is modelled by a stratified heterogeneous transmission structure. The application of the transverse operator method (TOM) on the multi-layered coaxial cell allowed the determination of the propagation constant of fundamental mode and its corresponding field distribution of the electromagnetic fields, and the characteristics of higher-order modes for the need of the characterization of discontinuities between empty line and loaded line. In the case of the microstrip line, the use of the modified transverse resonance method (MTRM) allowed the determination of characteristics of the fundamental and higher order modes. Since each cell consists of several different sections, the matrix S of the set will be determined by the use of the several modal methods, such as modal connection method (''mode matching'') and multimodal variational method (MVM). The direct analysis codes are coupled with several optimization programs to constitute the software for extracting the material parameters. These are applied to material samples in cylinder form holed by the coaxial cell, or thin rectangular wafer by the microstrip line. Broadband extraction results were obtained, values are comparable with those published. Both high-loss dielectrics and nanostructured materials have been studied by our method

Radar cross section studies

The ultimate goal is to generate experimental techniques and computer codes of rather general capability that would enable the aerospace industry to evaluate the scattering properties of aerodynamic shapes. Another goal involves developing an understanding of scattering mechanisms so that modification of the vehicular structure could be introduced within constraints set by aerodynamics. The development of indoor scattering measurement systems with special attention given to the compact range is another goal. There has been considerable progress in advancing state-of-the-art scattering measurements and control and analysis of the electromagnetic scattering from general targets