Date of Award

Spring 1-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Dejan S. Filipovic

Second Advisor

Gregor Lasser

Third Advisor

Scott Palo

Fourth Advisor

Alan Brannon

Fifth Advisor

W. Neill Kefauver

Abstract

This thesis presents the design of wideband, dual-polarized direction of arrival (DOA) antennas intended for use with digital processing backends. It is shown that using a digital receiver for DOA allows for wider bandwidth and improvement of the size, weight, and complexity of the antenna system at the cost of traditional design metrics. All antennas are designed using full-wave finite element simulations and are validated with measurements.

Four-arm modulated arm width (MAW) spiral antennas are analyzed for use as digital DOA sensors for linearly-polarized signals. Counter to traditional design procedures, tightly-wound MAW spirals with a small modulation ratio perform significantly better than both a MAW spiral with a large modulation ratio and a conventional spiral. The DOA performance is analyzed using the Cramer-Rao Lower Bound (CRLB). The low modulation ratio MAW spiral exhibits less than 1 degree of error over a plus/minus 30 degree elevation and 360 degree azimuth field of view and over a 4.6:1 bandwidth, while the other spirals are limited to about 2:1 bandwidth or less.

A 64-element circular array of tightly-coupled dipoles over a ground plane is analyzed and measured. The effects of the major features of the array are discussed. A dielectric slab ring is placed over the elements and extends outward past them to focus the fields of the antenna outward, as well as to lower the turn-on frequency of the array. The 64 elements are combined to four sectoral outputs, which can be used separately as part of a DOA sensor or combined in-phase for omnidirectional operation over a 3.45:1 bandwidth.

The horizontally-polarized circular array is integrated with a monocone and eight vertically-polarized tapered slot antennas (TSAs) to create a wideband dual-polarized DOA sensor. The monocone is isolated from the other elements by exploiting symmetry to cancel the coupling between the monocone and the TSAs, enabling the array to be used for simultaneous transmit and receive (STAR). The array achieves a wide bandwidth of 3.41:1 over which both return loss and isolation are high. The array is capable of providing high-accuracy DOA estimates over the entire upper hemisphere over its operating bandwidth, as characterized by the CRLB.

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