Novel Techniques for the Design and Characterization of Electromagnetic Devices with Application to Multilayer Structures and Waveguide Filters

Abstract

In this work, optimization methods are presented for the analysis of inverse and design problems in electromagnetics. The current and future demands placed on design engineers necessitate the hybridization of forward solvers (e.g., computational and empir- ical methods) with novel optimization algorithms to yield engineering development and analysis tools which are largely autonomous and not restricted to the familiar principles employed in traditional design work. Two specific problems are addressed to demonstrate the capabilities of the proposed methods.

First, several optimization algorithms (i.e., Sequential Quadratic Programming, the Genetic Algorithm, and Particle Swarm Optimization) are presented for the estimation of complex constitutive parameters of multilayered materials. Using X band waveguide S-parameter measurements, the complex constitutive parameters of each individual layer are extracted. The results are compared to measurements as well as those of single layer techniques which estimate the constitutive parameters of individual materials.

The second problem addressed is the automated design of waveguide filters. Initially, a study is conducted into whether dielectric slabs randomly doped with conducting in- clusions such as short, thin wires or thin patches could yield useful frequency dependent reflection and transmission behaviors when placed inside a waveguide. Results obtained by placing conducting patches on the slab’s surface were found promising. Therefore, op- timization techniques were then employed to find the appropriate arrangement of patches of the dielectric’s surface so that the resulting transmission response closely matched the response specified by the user. Results of this study were verified by fabrication and measurement for X band filters and, in all cases, found to be in excellent agreement.