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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
The Game As Life - Life As Game (GALLAG) project investigates how people might change their lives if they think of and/or experience their life as a game. The GALLAG system aims to help people reach their personal goals through the use of context-aware computing, and tailored games and applications. To accomplish this, the GALLAG system uses a combination of sensing technologies, remote audio/video feedback, mobile devices and an application programming interface (API) to empower users to create their own context-aware applications. However, the API requires programming through source code, a task that is too complicated and abstract for many users. This thesis presents GALLAG Strip, a novel approach to programming sensor-based context-aware applications that combines the Programming With Demonstration technique and a mobile device to enable users to experience their applications as they program them. GALLAG Strip lets users create sensor-based context-aware applications in an intuitive and appealing way without the need of computer programming skills; instead, they program their applications by physically demonstrating their envisioned interactions within a space using the same interface that they will later use to interact with the system, that is, using GALLAG-compatible sensors and mobile devices. GALLAG Strip was evaluated through a study with end users in a real world setting, measuring their ability to program simple and complex applications accurately and in a timely manner. The evaluation also comprises a benchmark with expert GALLAG system programmers in creating the same applications. Data and feedback collected from the study show that GALLAG Strip successfully allows users to create sensor-based context-aware applications easily and accurately without the need of prior programming skills currently required by the GALLAG system and enables them to create almost all of their envisioned applications.
ContributorsGarduno Massieu, Luis (Author) / Burleson, Winslow (Thesis advisor) / Hekler, Eric (Committee member) / Gupta, Sandeep (Committee member) / Arizona State University (Publisher)
Created2012
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
Improving accessibility to public buildings by people with special needs has been an important societal commitment that is mandated by federal laws. In the information age, accessibility can mean more than simply providing physical accommodations like ramps for wheel-chairs. Better yet, accessibility will be fundamentally improved, if a user can be made aware of important location-specific information like functions of offices near the user within a building. A smart environment may help a new person quickly get acquainted about the environment. Such features can be more critical for cases of making an indoor environment more accessible to people with visual impairment. With the intention to promote the integration of visually impaired people in society, this thesis efforts on methodologies for building smart and accessible indoor office environments with the help of Apple's Bluetooth Low Energy (BLE) technology called iBeacon to provide location awareness and enable easy access to information about the environment to people with visual impairment. This thesis presents work done on developing an iterative based approach in improving the configuration of given number of iBeacons to gain optimal signal coverage in a given office space environment and enabling smart features such as tagging points of interest and push notifications. This work aims to exploit the idea to look at visual impairment beyond the level of disability and cash it at as an opportunity to bring about a change of style of living. This work develops a methodology by introducing an end-to-end systems that uses intelligent server side and visually-impaired-friendly client side interfaces to give a prototype of an assistive technology to help them do basic activities like getting familiarized about an office environment without the need for asking for assistance.
ContributorsLagisetty, Jashmi (Author) / Li, Baoxin (Thesis advisor) / Hedgpeth, Terri (Committee member) / Balasooriya, Janaka (Committee member) / Arizona State University (Publisher)
Created2017
Description
ABSTRACT
The present studies investigated the separate effects of two types of visual feedback delay – increased latency and decreased updating rate – on performance – both actual (e.g. response time) and subjective (i.e. rating of perceived input device performance) – in 2-dimensional pointing tasks using a mouse as an input device. The first sub-study examined the effects of increased latency on performance using two separate experiments. In the first experiment the effects of constant latency on performance were tested, wherein participants completed blocks of trials with a constant level of latency. Additionally, after each block, participants rated their subjective experience of the input device performance at each level of latency. The second experiment examined the effects of variable latency on performance, where latency was randomized within blocks of trials.
The second sub-study investigated the effects of decreased updating rates on performance in the same manner as the first study, wherein experiment one tested the effect of constant updating rate on performance as well as subjective rating, and experiment two tested the effect of variable updating rate on performance. The findings suggest that latency is negative correlated with actual performance as well as subjective ratings of performance, and updating rate is positively correlated with actual performance as well as subjective ratings of performance.
The present studies investigated the separate effects of two types of visual feedback delay – increased latency and decreased updating rate – on performance – both actual (e.g. response time) and subjective (i.e. rating of perceived input device performance) – in 2-dimensional pointing tasks using a mouse as an input device. The first sub-study examined the effects of increased latency on performance using two separate experiments. In the first experiment the effects of constant latency on performance were tested, wherein participants completed blocks of trials with a constant level of latency. Additionally, after each block, participants rated their subjective experience of the input device performance at each level of latency. The second experiment examined the effects of variable latency on performance, where latency was randomized within blocks of trials.
The second sub-study investigated the effects of decreased updating rates on performance in the same manner as the first study, wherein experiment one tested the effect of constant updating rate on performance as well as subjective rating, and experiment two tested the effect of variable updating rate on performance. The findings suggest that latency is negative correlated with actual performance as well as subjective ratings of performance, and updating rate is positively correlated with actual performance as well as subjective ratings of performance.
ContributorsBrady, Kyle J (Author) / Wu, Bing (Thesis advisor) / Hout, Michael C (Committee member) / Branaghan, Russell (Committee member) / Arizona State University (Publisher)
Created2015
Description
While significant qualitative, user study-focused research has been done on augmented reality, relatively few studies have been conducted on multiple, co-located synchronously collaborating users in augmented reality. Recognizing the need for more collaborative user studies in augmented reality and the value such studies present, a user study is conducted of collaborative decision-making in augmented reality to investigate the following research question: “Does presenting data visualizations in augmented reality influence the collaborative decision-making behaviors of a team?” This user study evaluates how viewing data visualizations with augmented reality headsets impacts collaboration in small teams compared to viewing together on a single 2D desktop monitor as a baseline. Teams of two participants performed closed and open-ended evaluation tasks to collaboratively analyze data visualized in both augmented reality and on a desktop monitor. Multiple means of collecting and analyzing data were employed to develop a well-rounded context for results and conclusions, including software logging of participant interactions, qualitative analysis of video recordings of participant sessions, and pre- and post-study participant questionnaires. The results indicate that augmented reality doesn’t significantly change the quantity of team member communication but does impact the means and strategies participants use to collaborate.
ContributorsKintscher, Michael (Author) / Bryan, Chris (Thesis advisor) / Amresh, Ashish (Thesis advisor) / Hansford, Dianne (Committee member) / Johnson, Erik (Committee member) / Arizona State University (Publisher)
Created2020
Description
Touch plays a vital role in maintaining human relationships through social andemotional communications. This research proposes a multi-modal haptic display
capable of generating vibrotactile and thermal haptic signals individually and simultaneously.
The main objective for creating this device is to explore the importance
of touch in social communication, which is absent in traditional communication
modes like a phone call or a video call. By studying how humans interpret
haptically generated messages, this research aims to create a new communication
channel for humans. This novel device will be worn on the user's forearm and has
a broad scope of applications such as navigation, social interactions, notifications,
health care, and education. The research methods include testing patterns in the
vibro-thermal modality while noting its realizability and accuracy. Different patterns
can be controlled and generated through an Android application connected to
the proposed device via Bluetooth. Experimental results indicate that the patterns
SINGLE TAP and HOLD/SQUEEZE were easily identifiable and more relatable to
social interactions. In contrast, other patterns like UP-DOWN, DOWN-UP, LEFTRIGHT,
LEFT-RIGHT, LEFT-DIAGONAL, and RIGHT-DIAGONAL were less
identifiable and less relatable to social interactions. Finally, design modifications
are required if complex social patterns are needed to be displayed on the forearm.
ContributorsGharat, Shubham Shriniwas (Author) / McDaniel, Troy (Thesis advisor) / Redkar, Sangram (Thesis advisor) / Zhang, Wenlong (Committee member) / Arizona State University (Publisher)
Created2021