Master of Science, University of Akron, 2017, Electrical Engineering

Radio frequency (RF) antenna array beamforming based on electronically steerable wideband phased-array apertures find applications in communications, radar, imaging and radio astronomy. High-bandwidth requirements for wideband RF applications necessitate hundreds of MHz or GHz frame-rates for the digital array processor. Systolic array architectures are often employed in multi-dimensional (MD) signal processing for linear and rectangular antenna arrays. Thus, this research used a FPGA hardware platform, the ROACH-2, which is equipped with a Xilinx Virtex-6 SX475T FPGA chip, and which is widely used in the field of radio astronomy. The research concentrated on the prospects of implementation of systolic array based MD beamformers on the ROACH-2, and on methods of extending the operating frequency to GHz range by using polyphase structures. The proposed systolic array architectures employ a differential form 2-D IIR frequency planar beam filter structure which is low in hardware utilization. The study highlights techniques that can be used to overcome the limitations of the ROACH-2 signal processing platform to achieve high operating frequencies.

Committee: Arjuna Madanayake (Advisor); Subramaniya Hariharan (Committee Member); Joan Carletta (Committee Member) Subjects: Communication; Electrical Engineering; Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2010, Electrical Engineering

This thesis explores the use of wide band log periodic dipole array (LPDA) antennas in direction finding systems. A wide band log periodic antenna will be constructed and tested to ensure hardware capability. A novel approach utilizing non-uniform spacing in a linear array will be used to improve the spatial resolution of the direction finding system. These specialized linear arrays are known as minimum redundancy or non-redundant linear arrays.

Committee: Ray Siferd PhD (Committee Chair); Ronald Riechers PhD (Committee Member); Saiyu Ren PhD (Committee Member); Marian Kazimierczuk PhD (Committee Member); John Bantle PhD (Committee Member); Kefu Xue PhD (Other) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Industrial and Systems Engineering

Applications of precise optical components with complex shapes are becoming more popular because of demands for more accurate, smaller size optical components. Although fabrication techniques of the components have advanced in recent years, only molding based methods are typically suitable for mass production. On the other hand, molding based methods are less capable of creating complex optical components. To deal with these limitations, a process based on nickel electroforming is introduced to replicate mold inserts directly from a plastic optical component, which itself can be fabricated by any fabrication methods with high flexibility. Then, using the plated mold insert in precision compression molding, the optical components are replicated. To investigate replication capabilities of the developed method in fabrication of plastic optical components, a polymethylmethacrylate (PMMA) microlens array was replicated to a nickel-plated mold first from another plastic microlens array then mass-produced using compression molding process. Properties of both microlens arrays, were investigated for geometrical accuracy, surface quality, and optical performance. The results demonstrated a promising technique to manufacture plastic optical component with high production rates. Fabrication capabilities of the method in production of infrared optics was also evaluated through producing an infrared microlens array from a plastic microlens array. Comparison between the fabricated infrared microlens array and the plastic microlens array in terms of geometry, surface quality, and optical performance has shown that it is a promising technique for replicating infrared microlens arrays. Using the developed method, a new fabrication method of non-planar optical component with large area was also proposed and demonstrated by producing micro feature on a cylindrical surface. The technique was capable to transfer micro-optical features from a planar surface, which is much easier to pro (open full item for complete abstract)

Committee: Allen Yi (Advisor); Jose Castro (Committee Member); Yannis Korkolis (Committee Member) Subjects: Engineering; Industrial Engineering; Mechanical Engineering; Optics; Plastics

Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

Typical radar systems are limited to energy distribution characteristics that are range independent. However, operators are generally interested in obtaining information at particular ranges and discarding elsewhere. It seems appropriate then to attempt to put energy solely at the range(s) of interest, thus minimizing exposure to clutter, jammers and other range-dependent interferences sources. The frequency diverse array (FDA) can provide a mechanism to achieve range-dependent beamforming and the spatial energy distribution properties are investigated on transmit and receive for different architectures herein. While simplified FDA receive architectures have been explored, they exclude the return signals from transmitters that are not frequency matched. This practice neglects practical consideration in receiver implementation and has motivated research to formulate a design that includes all frequencies. We present several receiver architectures for a uniform linear FDA, and compare the processing chain and spatial patterns in order to formulate an argument for the most efficient design to maximize gain on target. It may also be desirable to beamsteer in higher dimensionalities than a linear array affords, thus, the transmit and receive concept is extended to a generic planar array. This new architecture allows 3-D beamsteering in angle and range while maintaining practicality. The spatial patterns that arise are extremely unique and afford the radar designer an additional degree of freedom to develop operational strategy. The ability to simultaneously acquire, track, image and protect assets is a requirement of future fielded systems. The FDA architecture intrinsically covers multiple diversity domains and, therefore, naturally lends it self to a multi-mission, multi-mode adar scheme. A multiple beam technique that uses coding is suggested to advance this notion.

Committee: Brian Rigling PhD (Advisor); Douglas Petkie PhD (Committee Member); Fred Garber PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, Miami University, 2010, Chemistry and Biochemistry

Planar array infrared (PA-IR) spectroscopy has recently been employed as an alternative to Fourier transform infrared (FT-IR) spectroscopy for studies involving dynamic chemical events. At the onset of this thesis, most PA-IR instruments were grating-based, which typically provided a sufficient spectral resolution but a poor spectral coverage. The results of this thesis demonstrated that prism-based spectrographs can be viable alternatives to grating-based spectrographs when spectral coverage is more important than spectral resolution. Chapter 1 serves as an introduction into FT-IR and PA-IR spectroscopy. Chapter 2 focused on the development of macroscopic transmission prism-based spectrographs, Chapter 3 evaluated the performance of an attenuated total internal reflection (ATR)-PA-IR spectrograph, Chapter 4 investigated the potential for PA-IR microspectroscopy and Chapter 5 employed ATR-PA-IR spectroscopy as a detection technique for liquid chromatography. Chapter 6 deviates slightly from the rest of this thesis and involved comparing macro ATR-FT-IR and micro ATR-FT-IR imaging for the analysis of counterfeit pharmaceutical tablets.

Committee: Andre Sommer PhD (Advisor); Neil Danielson PhD (Committee Chair); Curtis Marcott PhD (Committee Member); Shouzhong Zou PhD (Committee Member); Lei Kerr PhD (Committee Member) Subjects: Chemistry