Date of Award

2019

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Electrical Engineering (MS)

Administrative Home Department

Department of Electrical and Computer Engineering

Advisor 1

Christopher Middlebrook

Committee Member 1

Durdu Guney

Committee Member 2

Miguel Levy

Committee Member 3

Warren Perger

Abstract

Passive phased antenna arrays are utilized in military and civilian radar systems to determine the received signal origination. Phased array placement for optimal reception is challenging due to the required supporting electronic hardware and the associated coaxial cabling that typically accompanies each antenna channel. Low noise amplifiers and frequency conversion hardware add size and complexity, limiting possible positions for phased array placement. Eliminating required phased array electronic subcomponents without sacrificing function would allow placement onto smaller agile platforms, such as unmanned systems and rapid deployment networks. Electro-optic (EO) antenna elements utilize an optical waveguide embedded between the antenna and ground plane that responds to the electric field received by the resonating antenna. Using EO antenna elements removes associated electronic hardware from antenna sites, thus simplifying advanced phased array technology. EO antenna elements modulate received signals directly into the optical domain where the low loss, electromagnetic immunity, low weight, and small size advantages of optical fiber can be utilized for antenna remoting. The combination of optical signals from EO antenna elements in Mach-Zehnder interferometers reduces the number of overall channels needed for a given radar system. The reduction of channels further serves to decrease the size, weight, cost, computation, and power requirements of the radar system.

This thesis details the design, fabrication, and characterization of EO phased arrays and prototype EO antenna elements, both as individual antenna elements and in a phased array configuration. Waveguide loss, refractive index, and EO coefficient measurements are made for individual EO antenna elements. Radio Frequency (RF) phase modulation emulating a changing angle of arrival is applied by direct injection to a two-element phased array of EO antenna elements. The system’s optical output is correlated to the array factor for a two-element phased array showing proof-of-concept that EO antenna elements can be used in direction finding applications. The sensitivity of EO antenna elements is analyzed and a new design for EO antenna elements with improved sensitivity is presented. The electric field distribution of a rectangular patch antenna at resonance was found to be useful for driving a push-pull Mach-Zehnder modulator, doubling the EO antenna element sensitivity.

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