FRACTAL-INSPIRED SUBWAVELENGTH GEOMETRIC INCLUSIONS FOR IMPROVEMENT OF HIGH-FREQUENCY ELECTROMAGNETIC DEVICES

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Smith, K. (2018). FRACTAL-INSPIRED SUBWAVELENGTH GEOMETRIC INCLUSIONS FOR IMPROVEMENT OF HIGH-FREQUENCY ELECTROMAGNETIC DEVICES. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

This dissertation presents research results demonstrating the efficacy of fractal-inspired subwavelength geometric inclusions for improvement of high-frequency electromagnetic devices. It begins with a review of the open literature in the area of fractal applications in antennas and metamaterials. This is followed by a detailed discussion of three high-frequency electromagnetic devices that demonstrate performance improvement through incorporation of subwavelength geometric design elements.The first of these devices is a spherical spiral metamaterial unit cell that was developed as a three-dimensional fractal expansion of the traditional split ring resonator, and is shown to be capable of producing broadband negative permeability, negative permittivity, or both, depending solely on the orientation of the unit cells with respect to the incident electric field.The second device is a ringed rectangular patch antenna that has four resonant frequencies. All four of these operative frequencies are shown to produce similar radiation patterns, which also closely match the pattern of a traditional patch antenna. Several minor geometric modifications of the basic shape of the device are also presented, and are shown to enable modification of the number of resonances, as well as tuning of frequencies of resonance.The third and final topic is a modified horn antenna that incorporates a spiral metamaterial as a phase-shifting device in order to achieve circularly polarized radiation. The handedness of the radiated wave is shown to be tunable through simple reorientation of the loading unit cells.In each of these cases, electrically-small geometric modification of existing device geometries is shown to greatly affect performance, either by increasing bandwidth, by inducing multiband behavior, or by enabling exotic radiation characteristics.

Details
Author

Smith, Kathryn

Title

FRACTAL-INSPIRED SUBWAVELENGTH GEOMETRIC INCLUSIONS FOR IMPROVEMENT OF HIGH-FREQUENCY ELECTROMAGNETIC DEVICES

Physical Description

1 online resource (119 pages) : PDF

Date

2018

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

This dissertation presents research results demonstrating the efficacy of fractal-inspired subwavelength geometric inclusions for improvement of high-frequency electromagnetic devices. It begins with a review of the open literature in the area of fractal applications in antennas and metamaterials. This is followed by a detailed discussion of three high-frequency electromagnetic devices that demonstrate performance improvement through incorporation of subwavelength geometric design elements.The first of these devices is a spherical spiral metamaterial unit cell that was developed as a three-dimensional fractal expansion of the traditional split ring resonator, and is shown to be capable of producing broadband negative permeability, negative permittivity, or both, depending solely on the orientation of the unit cells with respect to the incident electric field.The second device is a ringed rectangular patch antenna that has four resonant frequencies. All four of these operative frequencies are shown to produce similar radiation patterns, which also closely match the pattern of a traditional patch antenna. Several minor geometric modifications of the basic shape of the device are also presented, and are shown to enable modification of the number of resonances, as well as tuning of frequencies of resonance.The third and final topic is a modified horn antenna that incorporates a spiral metamaterial as a phase-shifting device in order to achieve circularly polarized radiation. The handedness of the radiated wave is shown to be tunable through simple reorientation of the loading unit cells.In each of these cases, electrically-small geometric modification of existing device geometries is shown to greatly affect performance, either by increasing bandwidth, by inducing multiband behavior, or by enabling exotic radiation characteristics.

Genre

doctoral dissertations

Subjects--Topics

Electromagnetism

Degree

Ph.D.

Keywords

Antennas
Fractals
Metamaterials

Subject Area

Electrical Engineering

Advisor(s)

Adams, Ryan

Committee Members

Weldon, Thomas
Kakad, Yogendra
Williams, Wesley

Degree Note

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2018.

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Rights Holder Information

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Identifier

Smith_uncc_0694D_11642

Permalink

http://hdl.handle.net/20.500.13093/etd:1531