A New Class of Resonant Metasurfaces Based on Highly Subwavelength Metamaterial-Lined Apertures and Metamaterial-Coated Discs

• Author / Creator

  Baladi, Elham

• This work presents analytical, numerical and experimental studies of a new class of resonant metasurfaces (MTSs), which may also be classified as miniaturized-element frequency selective surfaces (FSSs). The proposed MTS unit cells consist of circular aperture or disc resonators that are made subwavelength through the introduction of metamaterial (MTM) liners. First, the theory of reduced-frequency resonances in a circular aperture in a conducting screen lined using a layer of $\epsilon$-negative and near-zero (ENNZ) MTM is studied by treating the liner as a homogeneous and anisotropic medium. It is shown that an array of circular apertures in a conducting screen whose interior is lined through thin layers of ENNZ MTM liners demonstrates resonant transmission at frequencies that are well below the natural resonance frequencies of unlined circular apertures of the same size or diffraction anomalies. Resonant transmission below the natural resonance frequency allows the use of smaller resonators at the operating frequency, resulting in miniaturization of the MTS unit cells. This theory is then extended through the application of Babinet's principle to the design of miniaturized resonant discs loaded using $\mu$-negative and near-zero (MNNZ) MTM liners. A dual transmission-reflection spectrum is obtained at the reduced resonant modes of the metallic disc resonators, providing frequency-selective reflection through compact MTSs at microwave frequencies.Both the ENNZ and MNNZ liners in the proposed MTSs are realized through practical printed-circuit board (PCB) implementations. A homogenization scheme based on transmission-line studies of the liners is used to show that they provide the desired permittivity/permeability behaviour. Numerical and experimental studies are presented to verify the successful frequency-selective enhancement of transmission/reflection at the resonance frequencies of extremely subwavelength MTM-lined circular apertures/discs. As the transmission/reflection mechanism in such aperture/disc arrays does not rely on diffraction effects, and each resonator demonstrates isolated resonance behaviour, the resonators can be closely spaced, resulting in compact array sizes, which is important at RF/microwave frequencies. Furthermore, interesting Fano-shape transmission/reflection parameters are obtained at the resonance frequency of aperture/disc arrays, which may be beneficial for many applications. For example, this property has been used to design for strongly decoupled aperture resonators with slightly different resonance frequencies. Such isolated resonators are then used to design an imaging device that can magnify subwavelength conducting features to the far-field. The performance of this device has been verified numerically as well as experimentally. The Fano-shape reflection parameter in the disc array results in very-high transmission levels above the resonant reflection frequency, which is important for shielding applications that require the MTS to remain transparent outside the shielding band. Extremely subwavelength, dual-band MTS unit cells are also developed based on the proposed MNNZ MTM-lined disc resonators combined with a different disc resonator realized through the application of $\mu$-positive and large (MPL) liners. Practical MTS unit cell implementations are used throughout these studies, and homogenized sheet models are obtained to explain the resonance behaviour at different operating bands. The performance of the proposed dual-band MTSs is studied numerically as well as experimentally.

• Subjects / Keywords

  • ISM-band Shielding
  • Homogenization
  • Drude Model
  • Miniaturized Apertures
  • Resonant Apertures
  • TEM horn antenna
  • Dual-Band Metasurfaces
  • Metamaterials
  • Fano lineshape
  • ENG
  • Metasurfaces
  • Disc resonators
  • Generalized Sheet Transition Conditions (GSTCs)
  • Wood-Rayleigh Anomaly
  • Metafilm
  • Frequency Selective Surfaces
  • Anechoic chamber
  • MNG
  • Transmission Line Model
  • Metascreen
  • Metamaterial-coated
  • Extraordinary Transmission
  • Far-Field Imaging
  • Effective-medium parameters

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-4eav-pt54

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.