Engineering Commons^™

High Performance Rf Control Devices Using Capacitively Coupled Contacts (C3) Over Iii-N Heterostructures, Faisal Jahan

Theses and Dissertations

RF switches, power limiters and other control devices are essential components of modern RF systems. RF switches are important parts of wireless modules of various devices such as laptops, tablets, cell phones etc. and key components of satellites communication systems, radars, multi-band wireless and aerospace communications, phased array antennas. RF Power limiters (PL) are also important components of RF systems protecting linear amplifiers, detectors etc. from high-power stress. Traditionally, RF switches are fabricated using pin diodes or MEMS, Si MOSFETs or GaAs HEMTs. RF PLs are typically implemented using Schottky or pin-diodes. Traditional devices used in RF switch and PLs …

Iii-V Nitride Micro- And Nano-Scale Cantilevers For Multimodal Sensing Applications, Ehtesham Bin Quddus

Theses and Dissertations

Recent research trends in chemical and biological sensing have been geared toward developing molecular sensor devices that are fast, label free, miniaturized and portable. The performance of these devices can be dramatically improved by utilizing multimodal detection techniques, new materials and micro-/nanofabrication technologies. This is especially true for micro-/nanoscale cantilever sensors, which undergo changes in mechanical or electrical properties upon the specific binding of molecules. To develop the sensor devices with the above attributes, we utilized III-V nitride materials: InN nanowires for realizing nanoscale cantilevers and AlGaN/GaN heterostuctures with or without embedded HFETs, for developing microcantilevers. There are mainly two …

A Method For Evaluating Power Generation Concepts Considering The Optimal Concept Of Operations, Tianlei Zhang

Theses and Dissertations

When trying to select an appropriate power generation plant for a micro-grid power distribution system like an electric ship, designers must consider both the physical characteristics (e.g., weight, volume, power ratings) and performance characteristics (e.g., fuel consumption, quality of service) of all the design alternatives. Comparing the design alternatives in terms of the physical characteristics is relatively straightforward, but in terms of performance characteristics each design alternative has to be evaluated within its own optimal performance points to make a fair comparison. However, at present no effective method or software tools exist to enable this evaluation at the earliest design …

Ultrawideband (Uwb) And Reconfigurable Antennas - New Concepts For Conformal Load Bearing Antenna Structures (Clas), Nicholas Bishop

Theses and Dissertations

Conformal antennas have been increasingly playing an important role in a vast number wireless of communication applications. More specifically, Conformal Load Bearing Antenna Structures (CLAS) have drawn a great deal of interest among researchers and engineers because of their advantages of multiple functionality, e.g. antenna and structure both. The objectives of this thesis are to investigate and design innovative conformal Ultrawideband (UWB) endfire antenna arrays and reconfigurable aperture coupled pixel patch antennas both of which are good candidates for CLAS. First, a broadband VHF-UHF end-fire Yagi-Uda array is proposed for possible air vehicle integration and operation within the 240-465 MHz …

Efficient Generation Of Power In Medium Voltage Direct Current Systems: Variable Speed Operation And Rectifier Considerations, Dan Li

Theses and Dissertations

By investigating variable speed operation of an engine and different types of ac-dc rectifier topologies, this dissertation provides procedures to develop and implement efficient Medium Voltage Direct Current (MVDC) power systems. The research reported here offered solutions to the following issues:

1) Efficiency improvement of a gas turbine by running it in variable speed operation mode.

2) The advantages and disadvantages of different ac-dc rectifier topologies considering both the efficiency and rectifier performance (dc bus voltage regulation, weight/size/volume of passive components, number of semi-conductor devices, displacement power factor, complexity of control strategy, etc.)

3) Implementation of variable speed MVDC power …

Optimal Design And Control Of Dc-Dc Resonant Converters For Wireless Power Transfer Applications, Isaac Nam

Theses and Dissertations

Wireless power transfer (WPT) technology provides galvanic isolation for improved safety and also provides reliability by eliminating the need for dedicated connectors/adapters that can get damaged due to frequent usage. For these reasons, it has become popular in medical implant charging and electric vehicle (EV) charging. Beyond these niche applications, due to aesthetic features and convenience provided by the cord-free environment, it is rapidly becoming an attractive charging solution for various portable electronics as well as household appliances. However, currently available WPT technology demonstrates several shortcomings and various challenges due to allowed receiver position variation with respect to transmitter position. …

Passive Equalizer Topology Analysis For Signal Integrity Applications, Kuo-Lun Yen

Theses and Dissertations

In high-speed, high density PCB bus systems, high frequency signal losses and crosstalk can have great impacts on signal integrity and digital timing, which can distort transmitted signals, worsen eye diagrams, and attenuate signal amplitudes. Also, these impacts make digital signals and their energy smearing over multiple bit positions as known as jitters, and cause the phenomenon of inter-symbol interference (ISI) in digital signal transmissions.

The main objective of this thesis is to analyze and develop efficient topology circuits for compensating bus system high frequency losses by using equalization techniques. The thesis has focused on study of various practical and …