A characteristic mode perturbation approach for antenna loading design

Young, Matthew William

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https://hdl.handle.net/2142/88289 Copy

Description

Title

A characteristic mode perturbation approach for antenna loading design

Author(s)

Young, Matthew William

Issue Date

2015-07-16

Director of Research (if dissertation) or Advisor (if thesis)

Bernhard, Jennifer T.

Doctoral Committee Chair(s)

Bernhard, Jennifer T.

Committee Member(s)

• Franke, Steven J.
• Schutt-Ainé, José E.
• Gong, Songbin

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Antenna design
• Characteristic mode theory
• Perturbation theory
• Spiral antenna
• Reactive loading
• Radiation efficiency
• Compensation theorem

Abstract

Reactive loading is commonly applied to antennas to modify input impedance and radiation pattern properties. However, reactive loading design approaches based on experience, intuition, and modeling are challenged as the demand grows for antennas with increased functionality and performance. New systematic design methods are needed that can manage complicated performance tradeoffs while providing physical insight into the fundamental antenna operation. Characteristic mode theory has shown promise for systematic antenna design, yet significant limitations still exist that restrict its usefulness. The transformations of characteristic modes with respect to frequency or reactive loading are currently understood only qualitatively, and insight into their behavior must be developed through experience. In this thesis, a novel characteristic mode perturbation approach is developed that provides a quantitative description of how mode eigenvalues and eigencurrents transform under reactive loading and frequency variation. Analytical equations are derived using a novel application of eigenvalue perturbation theory to the characteristic mode problem. The equations characterize the effect of impedance loading on the characteristic mode eigenvalues and eigencurrents and reveal the explicit factors governing the mode transformations. Insight from the perturbation equations suggests a new characteristic mode design paradigm in which loading is used to control the eigencurrent contributions between modes. The new eigencurrent contribution perspective can be used to understand and solve loading problems that traditional characteristic mode theory cannot. The approach is used to design the reactive loading of an Archimedean spiral antenna to produce beam tilt or an endfire radiation pattern while maintaining desirable VSWR properties. Finally, the perturbation approach is used to analyze antenna loss and is applied to the analysis and improvement of antenna radiation efficiency.

Graduation Semester

2015-8

Type of Resource

text

Permalink

http://hdl.handle.net/2142/88289

Copyright and License Information

Copyright 2015 Matthew William Young

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