EFFICIENT OPTIMIZATION OF ANTENNA AND ELECTROMAGNETIC DEVICES AT MEDIUM, RADIO, AND OPTICAL FREQUENCIES

Open Access
Author:
Brocker, Donovan Edward
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 19, 2016
Committee Members:
  • Douglas Henry Werner, Dissertation Advisor
  • Douglas Henry Werner, Committee Chair
  • Ram Mohan Narayanan, Committee Member
  • Timothy Joseph Kane, Committee Member
  • Douglas Edward Wolfe, Outside Member
Keywords:
  • Antennas
  • Coal Mine Communications
  • Electromagnetic Absorbers
  • Gradient-Index Lenses
  • Transformation Optics
Abstract:
The fast growth of computer technology has led to aggressive advancement in engineering design, where in the past, analytical methods and/or intuitive trial and error through experiments were the most lucrative tools. Specifically in electromagnetics, powerful computers can be used to run simulation models subject to numerical solutions of Maxwell’s equations, providing extremely accurate predictions of the device performance. Growing computer resources also offer the ability to optimize devices via simulation, facilitating fine-tuning before fabrication. Hence, engineering design has drifted more and more towards computer modeling and optimization and has, in some cases, drifted away from intuition-based design and experimental fine-tuning. Although the former approach has the tendency to lower research and development costs and, at times, predict novel devices, the latter is still essential to the overall advancement of engineering design. With this in mind, this dissertation summarizes multiple efforts, ranging across many sub-fields of electromagnetics, where computer modeling and optimization was strongly coupled to intuitive design. This approach leads to efficient optimization of high performance designs that would likely not be possible with analytical or brute-force computer optimization alone. First, a hybrid approach combining transmission line equations and full-wave models is developed to optimize large communication networks in coal mines for emergency response applications. Secondly, a miniaturized dual-band antenna with an interdigitated slot load is proposed based on transmission line models and fine-tuned using computer simulation models. The antenna was fabricated and characterized, showing excellent agreement with simulation predictions. Next, an ultra-thin electromagnetic absorber design is proposed based on an equivalent circuit model. In particular, the circuit model is used to optimize the absorber design for wide bandwidth. Subsequently, the circuit model is used to simplify the optimization routine by cascading the scattering properties of the different absorber regions. Finally, gradient-index lens design methodology is developed based on transformation optics, enabling superior mono- and polychromatic lens performances.