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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Electrical and Computer Engineering

Year Degree Awarded

2015

Month Degree Awarded

September

First Advisor

Do-Hoon Kwon

Second Advisor

Ramakrishna Janaswamy

Third Advisor

Marinos N. Vouvakis

Fourth Advisor

Mark Tuominen

Subject Categories

Electromagnetics and Photonics

Abstract

Virtual antenna radiation at microwave frequencies using metamaterials is presented. Based on the transformation electromagnetics technique, the media embedding a physical antenna in a ground recess is designed such that the far-zone radiation pattern of a virtual antenna radiating above a flat conducting ground plane is reproduced. The antenna and a limited surrounding space above a ground plane is folded below the ground level, resulting in a physical antenna in a ground recess that is enclosed in transformation media. The electromagnetic specification of the media surrounding the physical antenna at the bottom of the recess is provided by a properly defined coordinate transformation.

A three-step design approach is followed. First, microstrip transmission-line metamaterials for a ground-recessed probe are designed and implemented for virtual source formation above the ground plane. Transmission-line metamaterial unit cell designs for the embedding media are shown. Virtual probe formation is validated using full-wave simulations. Measured field distributions over the fabricated metamaterial-surface for an embedded probe current radiating in a ground recess confirm formation of a virtual line source above the ground plane. As a next step, resonant inclusion-based metamaterials are designed for embedding a two-dimensional electric line source in a ground recess. Metamaterials are fabricated and assembled. Measured field distributions for an effective two-dimensional configuration confirm formation of a virtual line current above the ground plane. As a final extension to a three-dimensional configuration, design, fabrication, and measurement of an embedded monopole antenna in a ground recess is presented. Poorer performance was measured compared with the two-dimensional case. The complexity and material losses associated with resonator-based, negative-index metamaterials for multiple polarizations in three-dimensional applications were identified as main technical challenges.

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