Engineering Commons^™

Nanophotonics For Dark Materials, Filters, And Optical Magnetism, Mengren Man

Open Access Dissertations

Research on nanophotonic structures for three application areas is described, a near perfect optical absorber based on a graphene/dielectric stack, an ultraviolet bandpass filter formed with an aluminum/dielectric stack, and structures exhibiting homogenizable magnetic properties at infrared frequencies. The graphene stack can be treated as a effective, homogenized medium that can be designed to reflect little light and absorb an astoundingly high amount per unit thickness, making it an ideal dark material and providing a new avenue for photonic devices based on two-dimensional materials. Another material stack arrangement with thin layers of metal and insulator forms a multi-cavity filter that …

Design Of An Asymmetric Reluctance Machine For A Generator Application, Bryan David Marquet

Open Access Theses

This work compares an Asymmetric Reluctance Machine (ARM) to a Uniform air Gap Reluctance Machine (UGRM) for a generator application. The ARM employs an asymmetric rotor pole to increase machine performance, specifically increasing torque density. A multi-objective optimization is employed to minimize mass and loss subject to design constraints. Two machines are compared in terms of their Pareto-optimal fronts.

Coupled Resonator Based Wireless Power Transfer For Bioelectronics, Henry Mei

Open Access Dissertations

Implantable and wearable bioelectronics provide the ability to monitor and modulate physiological processes. They represent a promising set of technologies that can provide new treatment for patients or new tools for scientific discovery, such as in long-term studies involving small animals. As these technologies advance, two trends are clear, miniaturization and increased sophistication i.e. multiple channels, wireless bi-directional communication, and responsiveness (closed-loop devices). One primary challenge in realizing miniaturized and sophisticated bioelectronics is powering. Integration and development of wireless power transfer (WPT) technology, however, can overcome this challenge.

In this dissertation, I propose the use of coupled resonator WPT for …

Circular Bessel Field Statistics And The Pursuit Of Far-Subwavelength Resolution, Yulu Chen

Open Access Dissertations

The statistical description of wave propagation in random media is important for many applications. While polarized light in systems with weakly interacting scatterers and sufficient overall scatter has zero-mean circular Gaussian statistics, the underlying assumptions break down in the Anderson localization and weakly scattering regimes. Although probability density functions for wave intensity and amplitude exist beyond Gaussian statistics, suitable statistical descriptions for the field with strong and weak random scatter were unknown. The first analytical probability density function for the field that is effective in both the Anderson localization regime and the weakly scattering regime is derived by modeling the …

Microwave Chemical Sensing Using Overmoded T-Line Designs And Impact Of Real-Time Digitizer In The System, Yu-Ting Huang

Open Access Dissertations

Microwave spectrometers have unique advantages in the ability to determine high resolution features that are specific to a given chemical. Very sharp lines which correspond to quantum states of the chemical allow for unique identification of the chemical. Recent advances have shown the possibility of room temperature microwave spectroscopy analysis in which the data is collected in a short amount of time using broadband chirp pulse Fourier transform microwave (CP-FTMW) spectroscopy. In this report, we explore the design of reduced size spectrometers focusing on the reduction as well as expansion of operation frequency of the microwave analysis cell, where the …

High-Power Microwave/ Radio-Frequency Components, Circuits, And Subsystems For Next-Generation Wireless Radio Front-Ends, Kenle Chen

Open Access Dissertations

As the wireless communication systems evolve toward the future generation, intelligence will be the main signature/trend, well known as the concepts of cognitive and software-defined radios which offer ultimate data transmission speed, spectrum access, and user capacity. During this evolution, the human society may experience another round of `information revolution'. However, one of the major bottlenecks of this promotion lies in hardware realization, since all the aforementioned intelligent systems are required to cover a broad frequency range to support multiple communication bands and dissimilar standards. As the essential part of the hardware, power amplifiers (PAs) capable of operating over a …

A Dynamic Magnetic Equivalent Circuit Model For Design And Control Of Wound Rotor Synchronous Machines, Xiaoqi Wang

Open Access Dissertations

Recently, a new magnetic equivalent circuit (MEC) model was developed to support automated multi-objective design of wound-rotor synchronous machines (WRSMs). In this research, the MEC model and its application have been enhanced. Initial enhancement has focused on using the MEC model to explore machine design and control as a unified problem. Excitation strategies for optimal steady-state performance have been developed. The optimization is implemented in two phases. First, stator and field excitation at rated power is obtained as part of a WRSM design in which the objectives are to minimize machine mass and loss. Second, a map between current and …

Filter Synthesis And Design Techniques For Highly Adaptable Systems, Eric James Naglich

Open Access Dissertations

Software defined radio and cognitive radio (SDR/CR) are promising concepts toward more optimally using the electromagnetic spectrum for communications and data transfer. These systems are highly agile in terms of modulation technique and frequency of operation due to early digitization and software processing of received radio frequency signals. However, the front ends of SDR/CR systems often use static antennas and switched banks of static, wide bandwidth filters before the digitization process. These components limit the ability of SDR/CR systems to operate in environments with high levels of interference and are therefore a bottleneck in the path to achieving optimal adaptation …

Time Domain Simulation Of Novel Photovoltaic Materials, Haejun Chung

Open Access Theses

Thin-film silicon-based solar cells have operated far from the Shockley- Queisser limit in all experiments to date. Novel light-trapping structures, however, may help address this limitation. Finite-difference time domain simulation methods offer the potential to accurately determine the light-trapping potential of arbitrary dielectric structures, but suffer from materials modeling problems. In this thesis, existing dispersion models for novel photovoltaic materials will be reviewed, and a novel dispersion model, known as the quadratic complex rational function (QCRF), will be proposed. It has the advantage of accurately fitting experimental semiconductor dielectric values over a wide bandwidth in a numerically stable fashion. Applying …

The Design And Evaluation Of A 5.8 Ghz Laptop-Based Radar System, Kevin Chi-Ming Teng

Open Access Theses

This project involves design and analysis of a 5.8 GHz laptop-based radar system. The radar system measures Doppler, ranging and forming Synthetic Aperture Radar (SAR) images utilizing Matlab software provided from MIT Open Courseware and performs data acquisition and signal processing. The main purpose of this work is to bring new perspective to the existing radar project by increasing the ISM band frequency from 2.4 GHz to 5.8 GHz and to carry out a series of experiments on the implementation of the radar kit. Demonstrating the radar at higher operating frequency is capable of providing accurate data results in Doppler, …