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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Creators: Peterson, Cory
- Member of: ASU Electronic Theses and Dissertations
Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
Description
Ancient Mediterranean cultures incorporated equine iconography into their artistic repertoires, demonstrating the horse's importance not only as a beast of burden and war, but also as a visual symbol of wealth and prestige. Interaction between man and horse appears in clay as early as the third millennium BC, along with the early development of ancient Near Eastern cultures. Tactical evolution in Near Eastern warfare, particularly the eclipse of chariot forces by the rise of cavalry, coincided with the emergence of equestrian terracotta figurines and facilitated the popularity of horse and rider imagery. Cyprus' many city-kingdoms have yielded a vast, coroplastic corpus in both votive and mortuary contexts, including figurines of equestrian type. These terracottas are an important contribution to the understanding of ancient Cypriote cultures, cities and their coroplastic oeuvre.
While many studies of excavated terracottas include horse and rider figurines, only a limited number of these publications dedicate adequate analysis and interpretation. Ancient Marion is one of the Cypriote city-kingdoms producing a number of equestrian terracottas that are in need of further examination. By focusing on the unpublished horse and rider figurines from Marion, this paper will add to the conversation of Cyprus' inclusion of equestrian iconography in coroplastic production. Through thorough analysis of the horse and rider terracottas, specifically their plastic and stylistic components, this thesis establishes typologies, makes visual comparisons and demonstrates Marion's awareness of an equine vogue both in contemporary Cyprus and abroad. The horse and rider figurines of Marion are an important contribution to the better understanding of the city-kingdom and exemplify the inclusion of equestrian imagery within the context of ancient societies.
While many studies of excavated terracottas include horse and rider figurines, only a limited number of these publications dedicate adequate analysis and interpretation. Ancient Marion is one of the Cypriote city-kingdoms producing a number of equestrian terracottas that are in need of further examination. By focusing on the unpublished horse and rider figurines from Marion, this paper will add to the conversation of Cyprus' inclusion of equestrian iconography in coroplastic production. Through thorough analysis of the horse and rider terracottas, specifically their plastic and stylistic components, this thesis establishes typologies, makes visual comparisons and demonstrates Marion's awareness of an equine vogue both in contemporary Cyprus and abroad. The horse and rider figurines of Marion are an important contribution to the better understanding of the city-kingdom and exemplify the inclusion of equestrian imagery within the context of ancient societies.
ContributorsWalter, Chelsea (Author) / Serwint, Nancy (Thesis advisor) / Sweeney, Gray (Committee member) / Baldasso, Renzo (Committee member) / Arizona State University (Publisher)
Created2014
Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
In this thesis, a digital input class D audio amplifier system which has the ability
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
Description
There is an ongoing debate around the extent that anthropogenic processes influence both plant species distribution dynamics and plant biodiversity patterns. Past human food use may leave a strong legacy on not only the extent that food plants are dispersed and fill their potential geographic ranges, but also on food plant species richness in areas that have been densely populated by humans through time. The persistent legacy of plant domestication on contemporary species composition has been suggested to be significant in some regions. However, little is known about the effects that past human food use has had on the biogeography of the Sonoran Desert despite its rich cultural diversity and species richness. I used a combination of ecoinformatics, ethnobotanical, and archaeological data sources to quantitatively assess the impacts of pre-Columbian, and in some cases, more recent, human-mediated dispersal of food plants on the Sonoran Desert landscape. I found that (i) food plants do fill more of their potential geographic ranges than their un-used congeners, and that polyploidy, growth form, and life form are correlated with range filling and past food usage. I also found that (ii) both pre-Columbian and contemporary human population presence are correlated with relative food plant species richness. Thus, both past human food use and contemporary human activities may have influenced the geographic distribution of food plants at regional scales as well as species richness patterns. My research emphasizes that there is an interplay between ecological and anthropogenic processes, and that, therefore, humans must be considered as part of the landscape and included in ecological models.
ContributorsFlower, Carolyn (Author) / Blonder, Benjamin (Thesis advisor) / Hodgson, Wendy (Committee member) / Peeples, Matthew (Committee member) / Salywon, Andrew (Committee member) / Arizona State University (Publisher)
Created2019
Description
Prehistoric farmers in the semi-arid American Southwest were challenged by marked spatial and temporal variation in, and overall low levels of, precipitation with which to grow their crops. One strategy they employed was to modify their landscape with rock alignments in order to concentrate surface water flow on their fields. A second challenge that has been less focused on by archaeologists is the need to maintain soil fertility by replenishing nutrients removed from the soil by agricultural crops. Numerous studies have shown that rock alignments can result in long-lasting impacts on soil properties and fertility. However, the direction and magnitude of change is highly variable. While previous work has emphasized the importance of overland flow in replenishing soil nutrient pools, none have investigated the influence of eolian deposition as a contributor of mineral-derived nutrients. This thesis explores the effects of the construction of rock alignments, agricultural harvest, and eolian deposition on soil properties and fertility on Perry Mesa within the Agua Fria National Monument. This site experienced dramatic population increase in the late 1200s and marked depopulation in the early 1400s. Since that time, although agriculture ceased, the rock alignments have remains, continuing to influence runoff and sediment deposition. In the summer of 2009, I investigated deep soil properties and mineral-derived nutrients on fields near Pueblo La Plata, one of the largest pueblos on Perry Mesa. To examine the effects of rock alignments and agricultural harvest independent of one another, I sampled soils from replicated plots behind alignments paired with nearby plots that are not bordered by an alignment in both areas of high and low prehistoric agricultural intensity. I investigated soil provenance and the influence of deposition on mineral-derived nutrients through analysis of the chemical composition of the soil, bedrock and dust. Agricultural rock alignments were significantly associated with differences in soil texture, but neither rock alignments nor agricultural history were associated with significant differences in mineral-derived nutrients. Instead, eolian deposition may explain why nutrient pools are similar across agricultural history and rock alignment presence. Eolian deposition homogenized the surface soil, reducing the spatial heterogeneity of soils. Dust is important both as a parent material to the soils on Perry Mesa, and also a source of mineral-derived nutrients. This investigation suggests that prehistoric agriculture on Perry Mesa was not likely limited by long term soil fertility, but instead could have been sustained by eolian inputs.
ContributorsNakase, Dana Kozue (Author) / Hall, Sharon (Thesis advisor) / Spielmann, Katherine (Committee member) / Hartshorn, Anthony (Committee member) / Arizona State University (Publisher)
Created2012