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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
ABSTRACT
The absence of the consonant sound /p/ in Libyan Arabic leads Libyan speakers of English to pronounce /p/ as /b/. This study examines how Libyan Arabic speakers distinguish the English /p/ and /b/ in their production of L2 English. The study also examines the effect of the production contexts and the learning environment on two groups of Libyan Arabic speakers' attainment of the English /p/ in the USA and Libya. The study collected voice recordings of word-initial /p/ and /b/ in isolated-words, minimal pairs, and sentences in English from both Libyan Arabic speakers and American English speakers. The study also collected Libyan Arabic stop consonants /b/, /t/, /d/, /k/, and /g/ from the Libyan participants. The voice recording data were collected using the WhatsApp mobile application from all participants and the Libyan Arabic participants were also asked to fill an online survey. Using voice onset time (VOT) as a measurement tool, this study measured the English and Libyan Arabic data through Praat software. The findings show that most Libyan Arabic participants distinguish between /p/ and /b/, but they did not have as high VOT averages as the American participants' /p/. It also reveals that the production context, especially in minimal pairs and sentence contexts, has an effect on their participants' production. However, the learning environment does not have an effect on the Libyan participants' pronunciation of /p/ in this study.
The absence of the consonant sound /p/ in Libyan Arabic leads Libyan speakers of English to pronounce /p/ as /b/. This study examines how Libyan Arabic speakers distinguish the English /p/ and /b/ in their production of L2 English. The study also examines the effect of the production contexts and the learning environment on two groups of Libyan Arabic speakers' attainment of the English /p/ in the USA and Libya. The study collected voice recordings of word-initial /p/ and /b/ in isolated-words, minimal pairs, and sentences in English from both Libyan Arabic speakers and American English speakers. The study also collected Libyan Arabic stop consonants /b/, /t/, /d/, /k/, and /g/ from the Libyan participants. The voice recording data were collected using the WhatsApp mobile application from all participants and the Libyan Arabic participants were also asked to fill an online survey. Using voice onset time (VOT) as a measurement tool, this study measured the English and Libyan Arabic data through Praat software. The findings show that most Libyan Arabic participants distinguish between /p/ and /b/, but they did not have as high VOT averages as the American participants' /p/. It also reveals that the production context, especially in minimal pairs and sentence contexts, has an effect on their participants' production. However, the learning environment does not have an effect on the Libyan participants' pronunciation of /p/ in this study.
ContributorsGarib, Ali A. A (Author) / Pruitt, Kathryn (Thesis advisor) / Renaud, Claire (Committee member) / González López, Verónica (Committee member) / Arizona State University (Publisher)
Created2014
Description
Using Spencer-Oatey's rapport management approach, the present study evaluates the interlanguage pragmatic development of 17 native English-speaking American learners over the course of a semester in Spain, specifically in terms of the strategies they used in their second language (L2) to manage rapport in an advice-giving, oral role-play situation at semester start and semester end. To allow for a more in-depth analysis of the effect that a semester abroad has on Spanish L2 advice-giving behaviors, the learners were grouped into two distinct proficiency levels. Group 1 (n=9) represents learners who entered the semester abroad with a beginning to intermediate-low proficiency level and group 2 (n=8) represents learners who entered the semester abroad with an intermediate-high proficiency level. The results indicate that both learner groups had similar overarching behavioral expectations in this context. Specifically, both sets of learners expressed empathy, involvement, and respect for the interlocutor, while at the same time they used advice-giving strategies of varied illocutionary force to claim authority in addressing the interlocutor's dilemma. Both groups also balanced face sensitivities through strategies that both enhanced and challenged the interlocutor's identity face. However, it is argued that in this context claiming authority and challenging the interlocutor's identity face were permitted behaviors that emphasized the relational goals of the participants. Additionally, when developmental differences between the two proficiency levels were analyzed, the results showed that learner proficiency had an impact on specific strategy choices.
ContributorsBaca, Evelyn C. (Author) / García, Carmen (Thesis advisor) / Lafford, Barbara (Thesis advisor) / Elorrieta, Jabier (Committee member) / Arizona State University (Publisher)
Created2011
Description
This semester-long study examined the functions for which English (L1) and Spanish (L2) were used in two intact hybrid Spanish as a foreign language (FL) university classes at the 202 (fourth semester) level. Five 75-minutes classes of two instructors were observed by the researcher, video- and audio-recorded, and transcribed. A survey was also used to determine the functions for which the instructors and students believed that Spanish and English were used in the classroom, and the functions for which both believed that the two languages should be used. Talking about a test and teaching grammar were the functions for which both instructors used the most English and the most Spanish. The questionnaire results indicated that the students who heard more Spanish in the classroom would have preferred that their instructor had used less Spanish for the functions of checking how well students understand a reading in class as well as when giving instructions or explaining how to do group activities. The Minnesota Language Proficiency Assessment for listening at the Intermediate-High level was administered to the students of both instructors at the beginning and at the end of the semester. The classroom observations indicated that although both instructors used more than 50% words in English during their classes, one instructor used twice as many words in Spanish as did the other. However, the results of the study revealed no significant relationship between the amount of Spanish used by the instructors in the classroom and the students' progress on listening proficiency from the beginning to the end of the semester.
ContributorsHansel, Patsy (Author) / Lafford, Barbara A. (Thesis advisor) / García, Carmen (Thesis advisor) / Elorrieta, Jabier (Committee member) / Arizona State University (Publisher)
Created2012
Description
This investigation's goal was to add to the small body of research on pragmalinguistic acquisition of L2 Spanish. Specifically, it centered on the production of complaints in Spanish. Data was collected via a written Discourse Completion Task (DCT) of a complaint-provoking situation presented in a website voiceboard to two non-native speaker (NNS) students groups of different proficiency levels and to a native speaker (NS) control group. The lower proficiency group was comprised of 11 NNS enrolled in a 200 level beginning/intermediate Spanish grammar class and the advanced proficiency group of 11 NNS enrolled in a 400 level advanced Spanish conversation and composition class. Neither group contained any participants who had studied abroad or lived in a Spanish-speaking country for more than 3 months. The control group consisted of 10 NSs of Spanish who were all natives or current residents of Northern Mexico. Data from the DCT was categorized into strategies which were organized into Head Acts and Supporting Moves, Deference and Solidarity Politeness systems, according to the frameworks of Blum-Kulka, et al. (1989) and Scollon and Scollon (1983), respectively. The results of the analysis revealed that all three groups of participants have overarching similarities in the use of multiple Head Acts, some used several times throughout a response, to realize a complaint and used some Supporting Moves to mitigate these Head Acts. The lower proficiency group diverged from the advanced proficiency group and NS control group in that lower proficiency students not only used a fewer total strategies and strategy types, but also preferred Head Acts and Supporting Moves that expressed discomfort or dislike over strategies that expressed criticism, or requested a solution from the listener, these being the primary strategies preferred by the advanced proficiency and control group participants. It was also found that the percentage of Supporting Moves decreased with the raise in proficiency level, also. After a discussion of the results, pedagogical implications are given based on these results to help students notice and acquire pragmalinguistcally appropriate responses to complaint-provoking situations.
ContributorsMorningstar, Kira (Author) / Lafford, Barbara (Thesis advisor) / García Fernandez, Carmen (Thesis advisor) / Elorrieta, Jabier Elorrieta (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
ABSTRACT This study focuses on second language acquisition process amongst East Asian adult learners at an English and Culture Acquisition Program (ECAP) classroom. To understand their English learning experience, this study employs classroom observation, participant interview and document collection as research methods. The findings of this work suggest that ECAP does intend to help learners acquire English language proficiency in ways that were responsive to both the sociocultural backgrounds and individual needs of participants. ECAP also respects and promotes the learners' autonomy in the learning process. However, the program administrators and teachers still need to deepen their understanding of East Asian learners' sociocultural heritage and individual needs and improve facilitation accordingly.
ContributorsMi, Ximin (Author) / Danzig, Arnold (Thesis advisor) / Ovando, Carlos (Committee member) / Szecsy, Elsie (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study examined the development and acquisition of second language (L2) sounds by adult students enrolled in a communicative language program. The investigation explored the acquisition of L2 phones by analyzing the voice onset time (VOT) of word-initial voiceless stops in Spanish by native English speakers. A total of 40 subjects participated in the study and were divided into three groups; one group of students enrolled in a first semester course, another group of students enrolled in a third semester course, and the last group enrolled in a fifth semester course. The duration of VOT was compared between groups reading from a word list consisting of 60 words during the 13th to 15th weeks of the semester. Significant differences in VOT were found between the first and fifth semester groups, as well as the third and fifth semester groups suggesting that accurate acquisition of L2 phones and the formation of new phonetic categories are possible for late L2 learners in accordance with the Speech Learning Model.
ContributorsRussell, Nathan (Author) / Beaudrie, Sara (Thesis advisor) / Cerron-Palomino, Alvaro (Committee member) / Gradoville, Michael (Committee member) / Arizona State University (Publisher)
Created2018
Description
ABSTRACT
This qualitative study used a survey to investigate the attitudes and experiences of 44 Heritage learners (HLL) and non-Heritage learners (NHLL) in beginning-level Spanish courses with a mixed population (HLLs and NHLLs) in the same classroom. Specifically, the survey elicited data on their attitudes and experiences towards their own language skills in Spanish and English, their mixed beginning-level Spanish course, their personal reactions to mixed classes, and their attitudes toward classmates that belong to the other group (e.g., HLLs view of NHLLs). The findings of this study indicated that HLLs perceived their listening and speaking skills to be better than their literacy (reading and writing) skills, while NHLLs self-assessed their receptive skills (reading and listening) to be higher than their productive skills (speaking and writing). In addition, both groups expressed a positive attitude toward mixed beginning-level Spanish classes and noted specific advantages to learning in such an environment (e.g., the opportunity to learn about each other’s cultures, the fact that each group felt appreciated and valued by the other group) with very few disadvantages (e.g., HLLs had mixed opinions on the effect that a mixed class might have on a teacher’s expectation for how much material is covered and how thoroughly, while NHLLs mostly agreed that a teacher’s expectations would affect the breadth and depth of material covered; NHLLs thought the presence of HLLs in their class might negatively affect their grades). However, both groups indicated they would prefer to be in Spanish classes with members of their own group instead of in mixed classes (NHLLs affirmed this more than HLLs). This study concludes with a discussion of pedagogical implications, limitations of the study, and ideas for future research on this topic.
This qualitative study used a survey to investigate the attitudes and experiences of 44 Heritage learners (HLL) and non-Heritage learners (NHLL) in beginning-level Spanish courses with a mixed population (HLLs and NHLLs) in the same classroom. Specifically, the survey elicited data on their attitudes and experiences towards their own language skills in Spanish and English, their mixed beginning-level Spanish course, their personal reactions to mixed classes, and their attitudes toward classmates that belong to the other group (e.g., HLLs view of NHLLs). The findings of this study indicated that HLLs perceived their listening and speaking skills to be better than their literacy (reading and writing) skills, while NHLLs self-assessed their receptive skills (reading and listening) to be higher than their productive skills (speaking and writing). In addition, both groups expressed a positive attitude toward mixed beginning-level Spanish classes and noted specific advantages to learning in such an environment (e.g., the opportunity to learn about each other’s cultures, the fact that each group felt appreciated and valued by the other group) with very few disadvantages (e.g., HLLs had mixed opinions on the effect that a mixed class might have on a teacher’s expectation for how much material is covered and how thoroughly, while NHLLs mostly agreed that a teacher’s expectations would affect the breadth and depth of material covered; NHLLs thought the presence of HLLs in their class might negatively affect their grades). However, both groups indicated they would prefer to be in Spanish classes with members of their own group instead of in mixed classes (NHLLs affirmed this more than HLLs). This study concludes with a discussion of pedagogical implications, limitations of the study, and ideas for future research on this topic.
ContributorsDones-Herrera, Vilma (Author) / Lafford, Barbara A. (Thesis advisor) / Cerron-Palomino, Alvaro (Committee member) / González, Verónica (Committee member) / Arizona State University (Publisher)
Created2015
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