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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
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
National mandates to decrease suspension numbers have prompted school districts across the country to turn to a practice known as restorative justice as an alternative to removing students through suspension or referral to law enforcement for problematic behavior. This ethnographic case study examines school-based restorative justice programs as potentially disruptive social movements in dismantling the school-to-prison-pipeline through participatory analysis of one school’s implementation of Discipline that Restores.
Findings go beyond suspension numbers to discuss the promise inherent in the program’s validation of student lived experience using a disruptive framework within the greater context of the politics of care and the school-to-prison-pipeline. Findings analyze the intersection of race, power, and identity with the experience of care in defining community to illustrate some of the prominent structural impediments that continue to work to cap the program’s disruptive potential. This study argues that restorative justice, through the experience of care, has the potential to act as a disruptive force, but wrestles with the enormity of the larger structural investments required for authentic transformative and disruptive change to occur.
As the restorative justice movement gains steam, on-going critical analysis against a disruptive framework becomes necessary to ensure the future success of restorative discipline in disrupting the school-to-prison-pipeline.
Findings go beyond suspension numbers to discuss the promise inherent in the program’s validation of student lived experience using a disruptive framework within the greater context of the politics of care and the school-to-prison-pipeline. Findings analyze the intersection of race, power, and identity with the experience of care in defining community to illustrate some of the prominent structural impediments that continue to work to cap the program’s disruptive potential. This study argues that restorative justice, through the experience of care, has the potential to act as a disruptive force, but wrestles with the enormity of the larger structural investments required for authentic transformative and disruptive change to occur.
As the restorative justice movement gains steam, on-going critical analysis against a disruptive framework becomes necessary to ensure the future success of restorative discipline in disrupting the school-to-prison-pipeline.
ContributorsWeeks, Brianna Ruth (Author) / Cuadraz, Gloria (Thesis advisor) / Swadener, Elizabeth (Committee member) / Lopez, Vera (Committee member) / Arizona State University (Publisher)
Created2018
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
Calls for changes in science education over the last several decades have contributed to a changing landscape of undergraduate life science education. As opposed to simply lecturing at students and expecting them to recite science facts, there has been a strong push to make systemic changes so that students not only know pertinent science content, but also walk away with critical science process skills. There have been suggestions to create environments that focus on goals such as evaluating scientific evidence and explanations, understanding the development of scientific knowledge, and participating in scientific practice and discourse. As a part of the call for increases in student participation in science practice, we’ve seen suggestions to increase student exposure to the tools, techniques, and published research within various science fields. The use of primary scientific literature in the classroom is documented as being a tool to introduce students to the nature of scientific reasoning, experimental design, and knowledge creation and transformation. Many of the current studies on primary scientific literature in undergraduate courses report on intensive course designs in which students interact with the material with very specific goals, as outlined by the authors and researchers. We know less about the practices that take place in typical undergraduate settings. This exploratory study looks at information provided by a national sample of faculty that alludes to what sort of practices are taking place and the reasoning for doing so. Through analysis of both closed-ended and open-ended survey questions we have found that faculty are engaging students with primary scientific literature for many reasons and in a variety of ways. We have also attempted to characterize the way in which faculty view the body of scientific literature, as members of the research community. We discuss the implications of faculty views on the utility and value of the body of scientific literature. We also argue that those perceptions inform how the material is used in the undergraduate classroom.
ContributorsWagoner, Nevada (Author) / Brownell, Sara (Thesis advisor) / Maienschein, Jane (Thesis advisor) / Ellison, Karin (Committee member) / Arizona State University (Publisher)
Created2016
Description
Since the early 1980s spoken word has been on the rise as a highly influential performance art form. Concurrently, there has been an increase in literature on spoken word, which tends to focus on the critical performative and transformative potential of spoken word. These on-going discussions surrounding youth spoken word often fail to take into account the dynamic, relational, and transitional nature of power that constructs space and subjectivity in spoken word. This ethnographic study of one youth spoken word organization – Poetic Shift – in a southwestern urban area makes a conscious attempt to provide a nuanced, contradictory and partial analysis of space, place, and power in relation to youth spoken word and aspires to generate an understanding of how spaces designated for spoken word are dialectically (re)produced and maintain or subvert dominant relations of power through a constant stream of negotiations. This study aims to more explicitly examine the relationship between place and spoken word in effort to understand how one’s positionality impacts, and is impacted by, their involvement in youth spoken word.
Over the course of a 6-month period participant observation was conducted at two high school spoken word workshops and four interviews were completed with both teaching artists and young adult spoken word poets. Using spatial and critical pedagogy frameworks, this study found that Poetic Shift serves as a platform for youth to engage in the performative process of narratively constructing and reconfiguring their identities. Poetic Shift’s ideological position that attributes value and validation to the voices and lived experiences of each youth is an explicit rejection of the dominant paradigm of knowing that relegates some voices to a culture of silence. The point at which the present study deviated from most other literature on spoken word is where it offers a critique of Poetic Shift as a site of critical literacy and of the unreflexive rhetoric of student empowerment. The problematic presuppositions within the call for youth voice and in the linear, overly simplistic curriculum of Poetic Shift tend to reinforce the dominant relations of power.
Over the course of a 6-month period participant observation was conducted at two high school spoken word workshops and four interviews were completed with both teaching artists and young adult spoken word poets. Using spatial and critical pedagogy frameworks, this study found that Poetic Shift serves as a platform for youth to engage in the performative process of narratively constructing and reconfiguring their identities. Poetic Shift’s ideological position that attributes value and validation to the voices and lived experiences of each youth is an explicit rejection of the dominant paradigm of knowing that relegates some voices to a culture of silence. The point at which the present study deviated from most other literature on spoken word is where it offers a critique of Poetic Shift as a site of critical literacy and of the unreflexive rhetoric of student empowerment. The problematic presuppositions within the call for youth voice and in the linear, overly simplistic curriculum of Poetic Shift tend to reinforce the dominant relations of power.
ContributorsKesselring, Jenna (Author) / Nakagawa, Kathryn (Thesis advisor) / Cheng, Wendy (Thesis advisor) / Lee, Charles (Committee member) / Arizona State University (Publisher)
Created2016