The Use of Fractals and Non-Foster Circuits for Wideband Metamaterials and Antennas

Search for this publication on Google Scholar
Smith, K. (2015). The Use of Fractals and Non-Foster Circuits for Wideband Metamaterials and Antennas. Unc Charlotte Electronic Theses And Dissertations.
Download PDF

Analytics

50 views ◎
20 downloads ⇓


Abstract

Implementations of two methods for broadening the performance bandwidth of resonant electromagnetic structures are presented. The first method is the use of non-Foster loading elements, and the second method is the use of fractal geometries. Non-Foster loading is used in the context of negative permittivity and negative permeability metamaterials. A capacitively loaded strip unit cell with non-Foster loading is presented and the effects of parasitic resistances in the non-Foster element are explored, as well as the effect of variations in the test fixture. The unit cell is shown in simulation and measurement to exhibit sub-unity permittivity over a 133% bandwidth. A split ring resonator unit cell with non-Foster loading is presented next. The effects of parasitic resistance in the non-Foster element and variations in the test fixture are demonstrated for this unit cell, and the structure is shown in simulation to exhibit negative permeability over a bandwidth of 100%. Fractal geometries are utilized next, first in the context of a negative permittivity metamaterial unit cell, and then in the context of 3D-printable monopole antennas. The fractal metamaterial unit cell is shown to exhibit negative permittivity over a bandwidth of 6.4% in a coaxial test fixture, which is estimated, based on simulations, to correspond to a bandwidth of 32.9% in free space. Two fractal antennas are presented. The first is based on a branching cube pattern and is shown in simulation to have 181% bandwidth and poor polarization at high frequencies. The other is based on a branching cone pattern and shown in simulation and measurement to have ~180% bandwidth, and in simulation to have considerably better polarization than the cubic version.

Details
Author

Smith, Kathryn

Title

The Use of Fractals and Non-Foster Circuits for Wideband Metamaterials and Antennas

Physical Description

1 online resource (139 pages) : PDF

Date

2015

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

Implementations of two methods for broadening the performance bandwidth of resonant electromagnetic structures are presented. The first method is the use of non-Foster loading elements, and the second method is the use of fractal geometries. Non-Foster loading is used in the context of negative permittivity and negative permeability metamaterials. A capacitively loaded strip unit cell with non-Foster loading is presented and the effects of parasitic resistances in the non-Foster element are explored, as well as the effect of variations in the test fixture. The unit cell is shown in simulation and measurement to exhibit sub-unity permittivity over a 133% bandwidth. A split ring resonator unit cell with non-Foster loading is presented next. The effects of parasitic resistance in the non-Foster element and variations in the test fixture are demonstrated for this unit cell, and the structure is shown in simulation to exhibit negative permeability over a bandwidth of 100%. Fractal geometries are utilized next, first in the context of a negative permittivity metamaterial unit cell, and then in the context of 3D-printable monopole antennas. The fractal metamaterial unit cell is shown to exhibit negative permittivity over a bandwidth of 6.4% in a coaxial test fixture, which is estimated, based on simulations, to correspond to a bandwidth of 32.9% in free space. Two fractal antennas are presented. The first is based on a branching cube pattern and is shown in simulation to have 181% bandwidth and poor polarization at high frequencies. The other is based on a branching cone pattern and shown in simulation and measurement to have ~180% bandwidth, and in simulation to have considerably better polarization than the cubic version.

Genre

masters theses

Subjects--Topics

Electrical engineering

Degree

M.S.

Keywords

Fractals
Negative Permeability
Negative Permittivity
Non-Foster Loading
Wideband Antennas
Wideband Metamaterials

Subject Area

Electrical Engineering

Advisor(s)

Adams, Ryan

Committee Members

Weldon, Thomas
Miri, Mehdi

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2015.

Rights Statement

This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). For additional information, see http://rightsstatements.org/page/InC/1.0/.

Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Smith_uncc_0694N_10818

Permalink

http://hdl.handle.net/20.500.13093/etd:1572