Date of Award

8-12-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Systems Engineering

First Advisor

Hussain Al-Rizzo

Abstract

Miniaturized electromagnetic soft surfaces have promising applications in contemporary wideband portable wireless devices including, Multiple Input Multiple Output (MIMO) systems, dual frequency applications, and mutual coupling reduction among antennas in user terminals utilizing MIMO schemes such as in 4th generation Long-Term Evolution (4G-LTE). The use of textured metallic surfaces over grounded dielectric slab with vias for the suppression of electromagnetic wave propagation for applications including, but not limited to, mutual coupling reduction among closely-spaced antenna elements in antenna arrays, bandwidth enhancement, and gain enhancement has been extensively researched during the past two decades. In this dissertation, novel one-dimensional (1-D) periodic miniaturized planar soft surfaces are introduced to suppress surface waves in one direction. The proposed structures have been characterized using numerical simulations and measurements. They are inserted between two microstrip patch antenna elements to reduce mutual coupling. New dual bandgap designs of planar soft surfaces are also introduced, characterized and measured. Conventional planar soft surfaces suffer from large sizes in terms of guided wavelength (unit cell size is λ,_g/4), narrow bandwidth (≤, 4 %) defined for a suppression level below -10 dB. The miniaturized planar soft surfaces introduced in this dissertation are smaller compared with existing planar soft surfaces (unit cell size is λ,_g/8), wider in bandwidth (20%) defined for a suppression level below -20 dB. A new two-dimensional (2-D) Electromagnetic Bandgap (EBG) unit cell is introduced. It is miniaturized compared with the well-known mushroom-like EBG. The proposed structure, which suppresses wave propagation in two directions, has a small unit cell size in terms of guided wavelength (λ,_g/6), possessing 12 % bandgap bandwidth defined for suppression level below -20 dB.

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