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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 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
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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

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
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Description

The U.S. Navy and other amphibious military organizations utilize a derivation of the traditional side stroke called the Combat Side Stroke, or CSS, and tout it as the most efficient technique available. Citing its low aerobic requirements and slow yet powerful movements as superior to the traditionally-best front crawl (freestyle),

The U.S. Navy and other amphibious military organizations utilize a derivation of the traditional side stroke called the Combat Side Stroke, or CSS, and tout it as the most efficient technique available. Citing its low aerobic requirements and slow yet powerful movements as superior to the traditionally-best front crawl (freestyle), the CSS is the go-to stroke for any operation in the water. The purpose of this thesis is to apply principles of Industrial Engineering to a real-world situation not typically approached from a perspective of optimization. I will analyze pre-existing data about various swim strokes in order to compare them in terms of efficiency for different variables. These variables include calories burned, speed, and strokes per unit distance, as well as their interactions. Calories will be measured by heart rate monitors, converting BPM to calories burned. Speed will be measured by stopwatch and observer. Strokes per unit distance will be measured by observer. The strokes to be analyzed include the breast stroke, crawl stroke, butterfly, and combat side stroke. The goal is to informally test the U.S. Navy's claim that the combat side stroke is the optimum stroke to conserve energy while covering distance. Because of limitations in the scope of the project, analysis will be done using data collected from literary sources rather than through experimentation. This thesis will include a design of experiment to test the findings here in practical study. The main method of analysis will be linear programming, followed by hypothesis testing, culminating in a design of experiment for future progress on this topic.

ContributorsGoodsell, Kevin Lewis (Author) / McCarville, Daniel R. (Thesis director) / Kashiwagi, Jacob (Committee member) / Industrial, Systems (Contributor) / Barrett, The Honors College (Contributor)
Created2014-12
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Description
As single junction silicon based solar cells approach their Shockley\u2014Queasier (SQ) conversion efficiency limits, tandem solar cells (TSC) provide an attractive prospect for higher efficiency cells. Although TSCs have been shown to be more efficient, their higher fabrication costs are a limiting factor for their economic competitiveness and large-scale integration

As single junction silicon based solar cells approach their Shockley\u2014Queasier (SQ) conversion efficiency limits, tandem solar cells (TSC) provide an attractive prospect for higher efficiency cells. Although TSCs have been shown to be more efficient, their higher fabrication costs are a limiting factor for their economic competitiveness and large-scale integration in PV power systems. Current literature suggests that even with reduced costs of fabrication in the future, TSCs still offer no competitive benefit for integration in utility-scale systems and may yield minimal benefits only in places where area-related costs are high. This work investigates Balance of Systems (BoS) circumstances under which TSCs can attain economic viability in scenarios where the necessary technological advances are made to increase the efficiency of solar cells beyond the SQ limit.
ContributorsMugwisi, Ngoni (Author) / Holman, Zachary (Thesis director) / Phelan, Patrick (Committee member) / Industrial, Systems (Contributor) / Electrical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
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Description
The Performance Based Studies Research Studies Group (PBSRG) at Arizona State University (ASU) has been studying the cause of increased cost and time in construction and other projects for the last 20 years. Through two longitudinal studies with a group of owners in the state of Minnesota (400 tests over

The Performance Based Studies Research Studies Group (PBSRG) at Arizona State University (ASU) has been studying the cause of increased cost and time in construction and other projects for the last 20 years. Through two longitudinal studies with a group of owners in the state of Minnesota (400 tests over six years) and the US Army Medical Command (400 tests over four years), the client/buyer has been identified as the largest risk and source of project cost and time deviations. This has been confirmed by over 1,500 tests conducted over the past 20 years. The focus of this research effort is to analyze the economic and performance impact of a delivery process of construction called the Job Order Contracting (JOC) process, to evaluate the value (in terms of time, cost, and customer satisfaction) achieved when utilizing JOC over other traditional methods to complete projects. JOC's strength is that it minimizes the need for the owner to manage, direct and control (MDC) through a lengthy traditional process of design, bid, and award of a construction contract. The study identifies the potential economic savings of utilizing JOC. This paper looks at the results of an ongoing study surveying eight different public universities. The results of the research show that in comparison to more traditional models, JOC has large cost savings, and is preferable among most owners who have used multiple delivery systems.
ContributorsLi, Hao (Author) / Kashiwagi, Dean (Thesis director) / Kashiwagi, Jacob (Committee member) / Industrial, Systems (Contributor) / Department of Information Systems (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12