NOVEL META-SURFACE DESIGN SYNTHESIS VIA NATURE-INSPIRED OPTIMIZATION ALGORITHMS

Open Access
Author:
Bayraktar, Zikri
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 17, 2011
Committee Members:
  • Douglas Henry Werner, Dissertation Advisor
  • Douglas Henry Werner, Committee Chair
  • Pingjuan Li Werner, Committee Member
  • Victor P Pasko, Committee Member
  • Brian Lewis Weiner, Committee Member
  • Lyle Norman Long, Committee Member
Keywords:
  • meta-surface
  • artificial magnetic conductors
  • wind driven optimization
  • electromagnetic bandgap
  • optimization
  • magneto-dielectrics
Abstract:
Heuristic numerical optimization algorithms have been gaining interest over the years as the computational power of the digital computers increases at an unprecedented level every year. While mature techniques such as the Genetic Algorithm increase their application areas, researchers also try to come up with new algorithms by simply observing the highly tuned processes provided by the nature. In this dissertation, the well-known Genetic Algorithm (GA) will be utilized to tackle various novel electromagnetic optimization problems, along with parallel implementation of the Clonal Selection Algorithm (CLONALG) and newly introduced the Wind Driven Optimization (WDO) technique. The utility of the CLONALG parallelization and the efficiency of the WDO will be illustrated by applying them to multi-dimensional and multi-modal electromagnetics problems such as antenna design and metamaterial surface synthesis. One of the metamaterial application areas is the design synthesis of 90 degrees rotationally symmetric ultra-small unit cell artificial magnetic conducting (AMC) surfaces. AMCs are composite metallo-dielectric structures designed to behave as perfect magnetic conductors (PMC) over a certain frequency range, those exhibit a reflection coefficient magnitude of unity with an phase angle of zero degrees at the center of the band. The proposed designs consist of ultra small sized frequency selective surface (FSS) unit cells that are tightly packed and highly intertwined, yet achieve remarkable AMC band performance and field of view when compared to current state-of-the-art AMCs. In addition, planar double-sided AMC (DSAMC) structures are introduced and optimized as AMC ground planes for low profile antennas in composite platforms and separator slabs for vertical antenna applications. The proposed designs do not possess complete metallic ground planes, which makes them ideal for composite and multi-antenna systems. The versatility of the DSAMC slabs is also illustrated where designs with lossy impedance patches on one face of the slab can be optimized for absorber applications while the other face of the slab still exhibits properties of an AMC. Another metamaterial design synthesis targets optimization of metallo-dielectric slabs to act as low-loss matched impedance magneto-dielectric metamaterials (MIMDM). Such designs provide magneto-dielectric material properties over a certain frequency range, allowing miniaturization of planar antennas when used as substrates. Similarly, MIMDM slabs can be designed for the absorber applications, where design equations for synthesizing such absorber materials from MIMDM are established. Finally, small sized rotationally symmetric unit cells are designed and employed as planar electromagnetic bandgap structures for microstrip patch antenna mutual coupling reduction.