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Title:Characteristic mode theory for closely spaced dipole arrays
Author(s):King, Aaron J.
Director of Research:Bernhard, Jennifer T.
Doctoral Committee Chair(s):Bernhard, Jennifer T.
Doctoral Committee Member(s):Franke, Steven J.; Gong, Songbin; Wasserman, Daniel M.
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Antenna Arrays
Characteristic Mode Theory
Coupled Mode Theory
Abstract:Applications of antenna arrays, such as radar, benefit significantly from an array with wide operational bandwidth. In order to create these arrays, designers have traditionally relied on arraying relatively wideband antennas. Recently, planar arrays utilizing narrowband elements have been shown to exhibit good wideband behavior when the elements are spaced less than the typical half wavelength spacing used by designers. The reason behind this result is not clear. The phenomenon is investigated in this work through the lens of antenna characteristic modes. The modes of an array are calculated using the method of moments, and these modes are characterized by their radiative behavior. Additionally, the Q factor of these planar arrays is calculated using the Fourier transforms of the tangential fields at the aperture. In the process, the wideband behavior of these closely spaced arrays of dipoles is explained. These concepts are then translated to antenna design parameters such as element input impedance and array current distributions for beam scanning and sidelobe reduction. The modes are then calculated and interpreted for higher order dipole resonances to understand their behavior over a wide frequency band. Lastly, the modes of a dipole array with a backing ground plane are described. The result is a description of the physics of closely spaced arrays based on a set of orthogonal modes which allows antenna array designers to make informed design choices for wideband arrays before having to perform computationally expensive full-wave simulations on these electrically large structures.
Issue Date:2015-04-21
Type:Thesis
URI:http://hdl.handle.net/2142/78403
Rights Information:Copyright 2015 Aaron J. King
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015


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