Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007. / Tentzeris, Manos, Committee Member ; Wollack, Edward, Committee Member ; Cressler, John, Committee Member ; Papapolymerou, Ioannis, Committee Chair ; Laskar, Joy, Committee Co-Chair ; Ayazi, Farrokh, Committee Member.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references. Also available in electronic version.

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The Gallium Arsenide Field Effect transistor (GaAs FET) is experiencing a widespread acceptance in space and terrestrial systems due to its low noise, high gain and frequency characteristics unmatched by bipolar devices. This paper describes a design of a 4 GHz low noise amplifier with GaAs FETs using the scattering parameters method. Special attention is given to overall noise/gain optimization in the band of interest. The Smith Chart is used extensively to match the two-port device with microstrip networks. Analysis and performance of the amplifier are presented.

An accurate noise measurement is essential to a proper characterization of a noisy device. In the 1950s, the IRE first proposed the classical noise parameters for characterizing a noisy linear two-port network, and subsequently a measurement and extraction procedure. Since then, the task of accurately characterizing the parameters has always been challenging due to the sensitive nature of the noise parameters. This is especially so for an on-wafer device noise measurement, as opposed to that of a packaged device, due to various factors such as the lower noise level and losses in the signal path. Combined with the downscaling of the MOSFET technology in recent decades, which also improved the device's noise performance, they make noise measurement and characterization become even more difficult. A typical noise measurement starts with the calibration or characterization of the measurement system. This step is as important as the measurement itself in terms of the ultimate accuracy of the results. This thesis presents a noise receiver characterization method which improves upon existing methods by accurately taking into account the different reflection coefficient of the noise source between its hot and cold states. The improvement allows more precise determination of the receiver characterizations. Numerous studies have investigated the effect of the choice of the source terminations on the noise measurement results. These studies often provided contradicting suggestions on the selection techniques. In the thesis, a selection technique is proposed that allows quick determination of desirable terminations. Analyses using real measurement data on a 65 nm n-type MOSFET show that the proposed technique is able to provide terminations that yield noise parameters with smaller uncertainties relative to other terminations. / Thesis / Master of Applied Science (MASc)

Call number: LD2668 .T4 1952 M32 / Master of Science

Over the past decades, microwave sintering has been investigated, and the effects of microwave sintering have been demonstrated, however there is still uncertainty as to what is causing the enhancements known as the microwave effect . For a better understanding of the microwave effect , the effect of microwaves on the pore size distribution during densification has been investigated for submicron-sized zinc oxide (ZnO), which was sintered with conventional heating and varying amounts of microwave power but always maintaining exactly the same time-temperature profile. Initially, the density of the sintered samples was measured and compared; this proved that the densification of the hybrid sintered samples was increased and that the higher the level of microwaves used, the more it enhanced the densification. After this, the porosity was investigated through the use of nitrogen adsorption analysis, mercury porosimetry and Field Emission Gun Scanning Electron Microscopy (FEGSEM). Initially, it was found that sintering with microwaves reduces pores faster than for conventional sintering as expected. However, the experiments also revealed that the mechanisms of the reduction in the porosity were not different for microwave sintering compared to conventional sintering. When the porosity was compared at equivalent densities, it was observed that there was no significant difference, either in terms of the amount of porosity or the microstructure development. Since the structural development was the same for both conventional and hybrid sintering, it was concluded that the cause for the enhancement of the densification was enhanced diffusion caused by an additional driving force induced by the microwave field. The investigation of the solid-state reaction between zinc oxide and alumina was designed to investigate whether the diffusion associated with reactions was also enhanced by the use of microwaves. Therefore, zinc oxide and alumina samples were reacted as diffusion couples using conventional and hybrid heating, the latter with varying amounts of microwave power. The analyses of the reaction layer using FEGSEM showed an increase in the reaction product layer thickness when hybrid heating was used, with a higher level of microwaves yielding more growth. These results supported the view that the enhanced reaction rates were caused by enhanced diffusion, again caused by an additional driving force induced by the microwave field. For both the densification and reaction cases, the most likely additional driving force is considered to be the ponderomotive effect.

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

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