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Electrical properties of Si- and Mg-doped InAs epitaxial layers grown by MOCVD were studied by performing magneto-transport measurements at different temperatures, from 300 K down to 1.2 K. The longitudinal magnetoresistance and Hall effect indicate a three-band system existing in n-type (p-type) InAs, which consists of the surface accumulation (inversion) layer, the bulk electron (hole) layer, and the nucleation layer. Therefore, a classical parabolic background in magnetoresistance due to multi-carrier occurs at low fields. With the magnetic field being further applied, a linear magnetoresistance caused by inhomogeneities is revealed. At liquid helium temperature, the Shubnikov-de Haas magneto-oscillations are also observed. These transport characterizations provide a means of analyzing the band structure at the InAs surface. In a set of n-type InAs epilayers with Si doped at different levels, the bulk electron density increases as the doping level increases. The increased ionized impurities lead to lower electron mobilities due to more Coulomb scatterings. For all the n-type InAs films, except the two active layers (surface and the bulk), the nucleation layer contributes to the film conductivity as well with an electron density of ~ 5 x 10¹⁷ cm⁻³ and a mobility of ~ 2000 cm²}/Vs. In a cooldown process, the electron density of each layer slightly and monotonically decreases whereas the mobility experiences a maximum from the competition between phonon scatterings and Coulomb scatterings. The phonon scattering overwhelms the Coulomb scatting at high temperatures, but declines as temperature decreases, thus the mobility increases. Around 100 K, the temperature-independent ionized impurity scattering becomes comparable with and starts exceeding the phonon scattering, as temperature further lowered, the screening effect of the Coulomb scattering is weakened because of the decreased carrier densities. As a result, the mobility starts dropping. The maximum mobility corresponds to a minimum resistance, which explains the non-trivial temperature dependence of the resistance in the cooldown history. For the p-type InAs film, the doping with Mg in the course of MOCVD growth allows us to obtain a large hole density and a low mobility at 300 K. At low temperatures, holes are frozen out, and a strong negative magnetoresistance with a dip at 0 field are observed, which is the antilocalization signal from accumulation electrons. This is a strong technique to probe the surface quantum states and derive the phase coherence length and the spin flip length of surface electrons. / Master of Science

The rise of satellites in Low Earth Orbit (LEO) is causing more terrestrial electromagnetic interference in the important L- and X-band frequencies which are crucial for astronomical observations. This thesis introduces reflectarray design which can serve as a basis for an interference mitigation solution for radio telescopes. In the envisioned application, When the reflectarray is placed around the circumference of an existing radio telescope, it can drive a null into the radio telescopes radiation pattern sidelobe distribution. Since the reflectarray only occupies a small potion of the rim of the paraboloidal main reflector, its presence does not significantly effect the main lobe peak gain. Since Iridium and Starlink are the target mega-constellations, the reflectarray must be dual band. To cover the operational bandwidths of these constellations, the target bandwidth in the L-band (Iridium) is 0.7%, and that in the X-band (Starlink) is 17.1%. This makes the design of the reflectarray challenging as the frequencies are widely separated and the bandwidth in the X-band is wide The work of this thesis marks a first step in this effort. It includes a reflectarray design containing a multi-layer stack consisting of: (1) a grounded substrate, (2) an X-band slot loaded unit cell geometry, (3) a dielectric superstrate, and (4) an L-band layer containing crossed dipoles. The dual band reflectarray is dual linearly polarized to maintain symmetric response. The reflectarray is designed and simulated using full-wave solvers. The results show that the reflectarray designs are capable of pattern shaping at both bands and operate across the required bandwidths. This architecture could serve as a basis for future reflectarrays capable of nulling satellite interference from mega-constellations in observatory applications in the future. / Master of Science / The signal clarity issues stemming from the increasing number of satellites in Low Earth Orbit (LEO), particularly in the vital L- and X-band frequencies essential for global communications and radio astronomy, are the motivation of this thesis. The endeavor concentrates on designing a dual-band dual-polarized reflectarray antenna which may ultimately be used to help mitigate interference in these bands in radio telescopes. The work is focused on the frequency ranges utilized by the major satellite networks Iridium and Starlink, which operate within the L-band (1616-1626.5 MHz) and X-band (10.7-12.7 GHz). Recognizing the significance of these frequencies for global communication and also to radio astronomy, the reflectarray is designed to contribute to a an interference mitigation system which would ultimately allow for coexistence between radio telescopes and communications systems satellites. Targeting bandwidth achievements of 0.7% for the L-band and 17.1% for the X-band, the focus is on nulling interference arising across these frequency bands and thereby increasing the sensitivity of the radio telescope operating amongst these mega-constellations. The thesis documents a multilayered reflectarray antenna, containing a wide-band X-band layer of slot antennas on one layer and an L-band superstrate layer containing crossed dipoles at another, both of which utilize dual linear polarization for symmetric operation. The completed reflectarray can operate simultaneously in both bands. It has been shown in the two papers cited by {ellingson2021sidelobe,budhu2024design} that reflectarrays placed along the rim of radio telescopes main reflector can be used to drive nulls in the sidelobe envelope of its radiation pattern thereby nulling incoming interference. The antenna design of this thesis suggests a possible candidate for these interference mitigation systems where both bands are targeted.

Master of Music / Department of Music / Frank C. Tracz / This report will present a detailed analysis of An English Folk Setting arranged by John Edmondson, A Childhood Hymn by David R. Holsinger, Mister Joe by Harold Bennett arranged by Larry Clark, and Celtic Air and Dance arranged by Michael Sweeney. The analyses are modeled on the “Teaching Music Through Performance in Band” series edited by Richard Miles, and the Macro-Micro-Macro score analysis form created by Dr. Frank Tracz. Chapter 2 will discuss the importance of music education as part of a well-rounded curriculum. Chapter 3 will discuss the importance of the use of quality literature, and how to determine if a piece of music is of high quality.

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / Changing from L/S-Band to C-Band requires not only new equipment. Even the characteristics of the new frequencies just as the new frequency environment are a challenge for the operations in this bands when changing from a well-known frequency environment to a unknown new one. This paper describes the way used at Airbus Defense and Space Flight Test Ground Station to get experience with new equipment and to learn more about the new environment. Repeatable and comparable tests allowed training for the operators and the optimization of the equipment and procedures with the new environment. Although many of the problems or features observed during the tests where expected in advance, but even unexpected results could be identified.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / Currently most of the missile telemetry systems operate in the lower S-Band frequency range (2200-2290 MHz). Due to Federal Government plans to repurpose this frequency spectrum to commercial entities, missile telemetry systems will have to migrate to operate in the lower C-Band range (4400-4940 MHz) as well. This move in the operational frequency requires the upgrading of not only the Range ground receiving equipment, but the airborne transmitting units as well. This paper will detail the efforts required to augment a missile telemetry unit from operating in S-Band to C-Band.

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