Engineering Commons^™

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 …

Techniques To Increase Computational Efficiency In Some Deterministic And Random Electromagnetic Propagation Problems, Selman Ozbayat

Open Access Dissertations

Efficient computation in deterministic and uncertain electromagnetic propagation environments, tackled by parabolic equation methods, is the subject of interest of this dissertation. Our work is comprised of two parts. In the first part we determine efficient absorbing boundary conditions for propagation over deterministic terrain and in the second part we study techniques for efficient quantification of random parameters/outputs in volume and surface based electromagnetic problems.

Domain truncation by transparent boundary conditions for open problems where parabolic equation is utilized to govern wave propagation are in general computationally costly. For the deterministic problem, we utilize two approximations to a convolution-in-space type …