Graduation Year

2019

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Thomas M. Weller, Ph.D.

Co-Major Professor

Gokhan Mumcu, Ph.D.

Committee Member

Larry Dunleavy, Ph.D.

Committee Member

Stephen Saddow, Ph.D.

Committee Member

Nathan Crane, Ph.D.

Committee Member

Dorothy Poppe, Ph.D.

Keywords

Three Dimensional Miniaturization, Ultra-Wideband Antennas, Interference Mitigation, Miniaturization Techniques, Notch Filter

Abstract

This work details the design and fabrication of an ultra-wideband periodic spiral antenna (PSA) with a notch filter embedded directly into the radiating aperture. Prototype fabrication of the PSA reveals long assembly time due to forming the antenna element, therefore modifications are made to allow fabricating the antenna elements on a thin, flexible, Polyimide substrate. A transmission line model is develop to support the updated configuration of the antenna elements. In addition, a symmetric spurline filter is integrated into the arms of the spiral antenna in order to address the common problem of interference in ultra-wideband systems. For the first time, a placement study is conducted to show the optimal location of the filter as a function of frequency. The presented transmission line model demonstrates the ability to decouple the design of the filter and antenna by being able to predict the resonant frequency and achieved rejection after integration of the two. Measured results show a gain rejection of 21 dB along with the ability to tune the resonance of the filter from 1.1 – 2.7 GHz using a lumped capacitor. For high power applications, thermal measurements are conducted, and for the first time, thermal profiles along the top of the antenna are used to show the radiation bands in a spiral antenna. Power tests are successfully conducted up to 40 W across the entire operational bandwidth and up to 60 W for 2 GHz and below. At these elevated power levels, a large voltage is generated across the lumped capacitor used to tune the resonance of the spurline filter; this issue is addressed through the development of a capacitive wedge that is overlapped on top of the spurline stub, which increases the voltage handling to 2,756 V. Measured results reveal a reduced tuning range compared to using lumped capacitors and a gain rejection of greater than 10 dB for all configurations.

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