Electrical & Computer Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2765
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Item A SUNLIGHT TO MICROWAVE POWER TRANSMISSION MODULE PROTOTYPE FOR SPACE SOLAR POWER(2013) Jaffe, Paul; Granatstein, Victor L; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The prospect of effectively limitless, continuous electricity from orbiting satellites for use on earth has captured many people's interest for decades. The proposed approach typically entails collection of solar energy, its conversion to microwave energy, and the wireless transmission of the microwaves to the earth. This offers the benefit of providing baseload power while avoiding diurnal cycle and atmospheric losses associated with terrestrial solar power. Proponents have contended that the implementation of such systems would offer energy security, environmental, and broad technological advantages to those who would undertake their development, while critics have pointed out economic, political, and logistical barriers. Niche applications, such as provision of power to remote military bases, might better tolerate the higher energy costs associated with early operational systems. Among recent implementations commonly proposed for solar power satellites, highly modular concepts have received considerable attention. Each employs an array of modules for performing conversion of sunlight into microwaves for transmission to earth. This work details results achieved in the design, development, integration, and testing of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for 2.45 GHz microwave-based "sandwich" module prototypes. Prototypes were fabricated and subjected to the challenging conditions inherent in the space environment, including solar concentration levels in which an array of modules might be required to operate. This testing of sandwich modules for solar power satellites in vacuum represents the first such effort. The effort culminated with two new sandwich module designs, "tile" and "step", each having respectively area-specific masses of 21.9 kg/m2 and 36.5 kg/m2, and mass-specific power figures of 4.5 W/kg at minimum one sun and 5.8 W/kg at minimum 2.2 suns (AM0) simulated solar illumination. The total combined sunlight to microwave efficiency of the modules was shown to be on the order of 8% and 7% for vacuum operation in the 10-6 torr regime. These represent the highest reported combined sandwich module efficiencies under either ambient or vacuum conditions, nearly quadrupling the previous efficiency record. The novel "step" concept was created to address thermal concerns and resulted in a patent publication. Results from module characterization are presented in context and compared with figures of merit, and practical thresholds are formulated and applied. The results and discussion presented provide an empirical basis for assessment of solar power satellite economic models, and point to several opportunities for improvements in area-specific mass, mass-specific power, and combined conversion efficiency of future prototypes.Item Characterization and Modeling of High Power Microwave Effects in CMOS Microelectronics(2010) Holloway, Michael Andrew; O'Shea, Patrick G; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The intentional use of high power microwave (HPM) signals to disrupt microelectronic systems is a substantial threat to vital infrastructure. Conventional methods to assess HPM threats involve empirical testing of electronic equipment, which provides no insight into fundamental mechanisms of HPM induced upset. The work presented in this dissertation is part of a broad effort to develop more effective means for HPM threat assessment. Comprehensive experimental evaluation of CMOS digital electronics was performed to provide critical information of the elementary mechanisms that govern the dynamics of HPM effects. Results show that electrostatic discharge (ESD) protection devices play a significant role in the behavior of circuits irradiated by HPM pulses. The PN junctions of the ESD protection devices distort HPM waveforms producing DC voltages at the input of the core logic elements, which produces output bit errors and abnormal circuit power dissipation. The dynamic capacitance of these devices combines with linear parasitic elements to create resonant structures that produce nonlinear circuit dynamics such as spurious oscillations. The insight into the fundamental mechanisms this research has revealed will contribute substantially to the broader effort aimed at identifying and mitigating susceptibilities in critical systems. Also presented in this work is a modeling technique based on scalable analytical circuit models that accounts for the non-quasi-static behavior of the ESD protection PN junctions. The results of circuit simulations employing these device models are in excellent agreement with experimental measurements, and are capable of predicting the threshold of effect for HPM driven non-linear circuit dynamics. For the first time, a deterministic method of evaluating HPM effects based on physical, scalable device parameters has been demonstrated. The modeling presented in this dissertation can be easily integrated into design cycles and will greatly aid the development of electronic systems with improved HPM immunity.Item Measurements of doping-dependent microwave nonlinear response in cuprate superconductors(2007-04-25) Mircea, Dragos Iulian; Anlage, Steven M; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Near-field microwave techniques have been successfully implemented in the past for the local investigation of magnetic materials and high-temperature superconductors. This dissertation reports on novel phase-sensitive linear- and nonlinear response microwave measurements of magnetic thin films and cuprate superconductors and their interpretation.