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- Genre: Masters Thesis
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- 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
Demands in file size and transfer rates for consumer-orientated products have escalated in recent times. This is primarily due to the emergence of high definition video content. Now factor in the consumer desire for convenience, and we find that wireless service is the most desired approach for inter-connectivity. Consumers expect wireless service to emulate wired service with little to virtually no difference in quality of service (QoS). The background section of this document examines the QoS requirements for wireless connectivity of high definition video applications. I then proceed to look at proposed solutions at the physical (PHY) and the media access control (MAC) layers as well as cross-layer schemes. These schemes are subsequently are evaluated in terms of usefulness in a multi-gigabit, 60 GHz wireless multimedia system targeting the average consumer. It is determined that a substantial gap in published literature exists pertinent to this application. Specifically, little or no work has been found that shows how an adaptive PHYMAC cross-layer solution that provides real-time compensation for varying channel conditions might be actually implemented. Further, no work has been found that shows results of such a model. This research proposes, develops and implements in Matlab code an alternate cross-layer solution that will provide acceptable QoS service for multimedia applications. Simulations using actual high definition video sequences are used to test the proposed solution. Results based on the average PSNR metric show that a quasi-adaptive algorithm provides greater than 7 dB of improvement over a non-adaptive approach while a fully-adaptive alogrithm provides over18 dB of improvement. The fully adaptive implementation has been conclusively shown to be superior to non-adaptive techniques and sufficiently superior to even quasi-adaptive algorithms.
ContributorsBosco, Bruce (Author) / Reisslein, Martin (Thesis advisor) / Tepedelenlioğlu, Cihan (Committee member) / Sen, Arunabha (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis describes research into the application of socially reflective, or "Slow", design principles to modern mediated systems, or "Fast" technology. The "information overload" caused by drastic changes in the nature of human communications in the last decade has become a serious problem, with many human-technology interactions creating mental confusion, personal discomfort and a sense of disconnection. Slow design principles aim to help create interactions that avoid these problems by increasing interaction richness, encouraging engagement with local communities, and promoting personal and communal reflection. Three major functional mediated systems were constructed to examine the application of Slow principles on multiple scales: KiteViz, Taskville and Your ____ Here. Each system was designed based on a survey of current research within the field and previous research results. KiteViz is a visually metaphorical display of Twitter activity within a small group, Taskville is a workplace game designed to support collaboration and group awareness in an enterprise, and Your ____ Here is a physical-digital projection system that augments built architecture with user-submitted content to promote discussion and reflection. Each system was tested with multiple users and user groups, the systems were evaluated for their effectiveness in supporting each of the tenets of Slow design, and the results were collected into a set of key findings. Each system was considered generally effective, with specific strengths varying. The thesis concludes with a framework of five major principles to be used in the design of modern, highly-mediated systems that still apply Slow design principles: design for fundamental understanding, handle complexity gracefully, Slow is a process of evolution and revelation, leverage groups and personal connections to encode value, and allow for participation across a widely distributed range of scales.
ContributorsLinn, Silvan (Author) / Kelliher, Aisling G (Thesis advisor) / Tinapple, David (Committee member) / Boradkar, Prasad (Committee member) / Arizona State University (Publisher)
Created2011
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
Contemporary cities are physical and virtual. This thesis describes the findings of a mixed-methods study concerning visual images of the city in the urban Northeast of the United States. I ground these approaches in existing literature concerning digital media, visual narrative, genre ecology, urban planning, and virtual places. The first part of the study analyzes the results of a survey in which 150 people responded to questions about social media use and the relationships between image type and the functions of social media in urban contexts. The second part of the study analyzes the results of coding one year of visual images tweeted by @CambMA, the municipal Twitter feed for the City of Cambridge, Massachusetts. These approaches required the development of new tools for analyzing visual communication and genre moves in specific media contexts. My research suggests that specific image types are suited for specific media functions in the context of visual communication in virtual urban environments and that some image types are especially effective in capturing and expressing the city. These findings provide potential strategies for municipal social media channels to consider in terms of how they communicate with their audiences.
ContributorsDel Nero, Zachary (Author) / Maid, Barry (Thesis advisor) / D'Angelo, Barbara (Committee member) / Mara, Andrew (Committee member) / Arizona State University (Publisher)
Created2019
Description
The current study investigated how multimedia pacing (learner-control versus system-paced) and presentation styles (visual-only versus audio/visual) impact learning physics concept material, mental effort, and self-efficacy. This 2X2 factorial study randomly assigned participants into one of four conditions that manipulated presentation style (visual-only versus audio/visual) and pacing of the content (system-paced versus learning-controlled). Participant's learning was measured by recording their retention of information and ability to transfer information. Measures of perceived difficulty (mental effort) and perceived ability (self-efficacy) were also obtained. No significant effects were observed in this study which doesn’t support the existence of either the modality or reverse modality effect at least in these noisier online learning environments. In addition, the hypothesis that their effects could be an artifact of experimental design could not be proven as the learner control condition did not yield any significant results.
ContributorsKrause, Tyler (Author) / Craig, Scotty D. (Thesis advisor) / Gray, Robert (Committee member) / Branaghan, Russell (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
The increased risk of falling and the worse ability to perform other daily physical activities in the elderly cause concern about monitoring and correcting basic everyday movement. In this thesis, a Kinect-based system was designed to assess one of the most important factors in balance control of human body when doing Sit-to-Stand (STS) movement: the postural symmetry in mediolateral direction. A symmetry score, calculated by the data obtained from a Kinect RGB-D camera, was proposed to reflect the mediolateral postural symmetry degree and was used to drive a real-time audio feedback designed in MAX/MSP to help users adjust themselves to perform their movement in a more symmetrical way during STS. The symmetry score was verified by calculating the Spearman correlation coefficient with the data obtained from Inertial Measurement Unit (IMU) sensor and got an average value at 0.732. Five healthy adults, four males and one female, with normal balance abilities and with no musculoskeletal disorders, were selected to participate in the experiment and the results showed that the low-cost Kinect-based system has the potential to train users to perform a more symmetrical movement in mediolateral direction during STS movement.
ContributorsZhou, Henghao (Author) / Turaga, Pavan (Thesis advisor) / Ingalls, Todd (Committee member) / Papandreou-Suppappola, Antonia (Committee member) / Arizona State University (Publisher)
Created2016
Description
Lesbian, gay, bisexual, transgender and queer (LGBTQ+) individuals experience a variety of types of representation, particularly in media outlets. While the quantity of such representations is steadily increasing, research must continue to examine the content of representations as they become available. This examination is important as much of society is determined by discourses presented in media outlets. Further, media often produces and reproduces dominant narratives about minority groups. Television is one arena where individuals come to learn about themselves and others. Particularly, the sitcom genre can be useful for figuring out how to deal with real-world issues in a humorous and entertaining way. However, the humor of sitcom does not exclude it from the meaning-making and identity-formation systems present in television and media, more broadly. Thus, this study investigates the discourses surrounding LGBTQ+ representation in the Canadian sitcom Schitt’s Creek through critical and rhetorical discursive analyses while also applying principles of queer theory throughout. Results indicate while Schitt’s Creek does many things well in terms of its representation of LGBTQ+ individuals, problematic stereotypes still often remain. In other words, Schitt’s Creek breaks from typical LGBTQ+ representation found in sitcoms, but often still embodies dominant cultural narratives used to degrade, restrict, and punish LGBTQ+ individuals. This is particularly evident as one examines the ways Schitt’s Creek often falls into heteronormative standards and continually polices the sexual nature of LGBTQ+ individuals to display a safe and comfortable version of homosexuality. Therefore, Schitt’s Creek may often and unknowingly reinforce the heteronormative hegemonies it seeks to break from.
ContributorsKiourkas, Steffanie M (Author) / Mean, Lindsey (Thesis advisor) / Walker, Michael (Committee member) / Gruber, Diane (Committee member) / Arizona State University (Publisher)
Created2023
Description
With widespread increases in the use of electronic communication technology, cyber-sexual harassment (CSH) has been on the rise. Broadly defined, CSH is unwelcome and repeated conduct of a sexual nature performed through electronic technology. The prevalence of CSH reported in previous studies varies significantly due in part to inconsistencies in how CSH is defined and measured. Whereas four existing scales measuring aspects of CSH have been published, each has several limitations. This research aims to develop and psychometrically validate the Multidimensional Cyber-Sexual Harassment Experiences and Attitudes Scale for Victimization (MCSHEA-V), which taps into five key components of CSH, including: (1) gathering sexual information online, (2) image and video-based sexual harassment, (3) offensive comments or posts, (4) coercive behaviors, and (5) CSH attitudes. In Study 1, a sample of psychology graduate students and faculty (N = 13) evaluated the content validity of the MCSHEA-V items, leading to key improvements in item relevance, clarity, and wording. In Study 2, a sample of adult participants (N = 298) completed the initial version of the scale through the online survey platform, Prolific.co. Confirmatory factor analyses indicated the proposed 5-factor structure was a good fit, but exploratory factor analyses indicated the items represented an alternative 4-factor structure. Specifically, these items captured dyadic CSH behaviors, CSH behaviors that affect one’s reputation, perceptions of the seriousness of CSH, and CSH victim-blaming behaviors. In Study 3, an additional sample of adult participants (N = 207) was surveyed via Prolific.co. Separate confirmatory factor analyses indicated the 4-factor model was the best fit. Overall, the MCSHEA-V will contribute to a clearer understanding of the defining features and prevalence of CSH victimization and facilitate future research through the introduction of a psychometrically-validated measurement tool.
ContributorsWheeler, Brittany (Author) / Hall, Deborah (Thesis advisor) / Mickelson, Kristin (Committee member) / Burleson, Mary (Committee member) / Arizona State University (Publisher)
Created2022