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Title:Reconfigurable antennas based on microplasma as a time-varying dielectric or conductor
Author(s):Yang, Hee Jun
Director of Research:Eden, J. Gary
Doctoral Committee Chair(s):Eden, J. Gary
Doctoral Committee Member(s):Bernhard, Jennifer; Kudeki, Erhan; Li, Xiuling; Ruzic, David; Park, Sung-Jin
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):Microplasma
Microplasma propagation
Plasma photonic crystal
Plasma antenna
Abstract:The theme of this dissertation is the applications of microcavity plasmas to electromagnetically active devices in the mm-wave and µ-wave regions. There are three accomplishments reported in this dissertation: microplasma on a chip, plasma photonic crystals, and microplasma antennas. Dynamic behaviors of microplasma packets were described using four different microchannel designs. An array of microplasma jets were used to demonstrate plasma photonic crystals exhibiting narrowband attenuation at 157 GHz. Using a conductor behavior of microplasma, the first planar type plasma antennas were introduced and demonstrated. First of all, four different designs of microchannels were explored and demonstrated including channels with different widths, spiral, Cornu spiral, and switchyard. Spatially periodic microplasma packets were observed in the microchannels with width between 300 and 700 µm. Circular shaped plasma packets were aligned at the center when the width was less than 450 µm; however, the shape transformed to triangular form and packets started to adhere to the adjacent wall due to the wall-plasma interaction. Two types of propagation in the spiral structure were also observed. Radial and azimuthal propagation velocities of 3 ±1 km/s and 8 ±1.5 km/s were recorded, respectively. From the Cornu spiral, ignition of the plasma at each of the center rings was observed due to the floating ground. In the switchyard design, the propagation starting point was controllable by inserting a sharp edge that causes the strongest electric field within the channels. In addition, a plasma photonic crystal exhibiting narrowband attenuation at 157 GHz has been demonstrated. Photonic crystals comprising Bragg layers of microplasmas interspaced with air were made with arrays of microplasma jets. Room temperature vulcanization silicone was solidified from the liquid form within specific shaped mold to guide an array of microplasma jets. The pitch and diameter of each microplasma jet are 1 mm and 400 µm, respectively. Microplasma jets were driven by 20 kHz sinusoidal voltage with helium flow rate of 10 lpm. Time-averaged attenuation of 5% at 157.0 GHz with narrow bandwidth (~ 1 GHz) has been observed. The position of the line center was accurately predicted by simulation; however, the simulated and measured magnitudes of the peak attenuation disagree due to the duty cycle and uniformity of the plasma columns. Lastly, this work introduced and demonstrated a first planar-type of plasma antenna. For a plasma patch antenna device, an aperture coupled feeding was chosen to avoid direct contact between the plasma and the microwave feeding line. Two or three layers of 1 mm quartz plates were used to generate plasma within quartz plates and FR-4 substrate was also used for the ground plane and the microstrip feeding line. Microplasma patch antenna data was compared with the simulation result. Also, a microplasma-enhanced patch antenna exhibiting 15% enhanced radiating power was observed at 5.12 GHz with an additional quartz layer with 12 mm x 12 mm copper patch. In summary, this dissertation unveils new microplasma applications on electromagnetic waves and explores the behavior of microplasmas in a variety of microchannels.
Issue Date:2019-12-02
Type:Text
URI:http://hdl.handle.net/2142/106471
Rights Information:Copyright 2019 Hee Jun Yang
Date Available in IDEALS:2020-03-02
Date Deposited:2019-12


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