Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Joseph Y. N. Hui. / M.S.

Fan Chun Wah. / "March 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. [140]-148). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Quadrature amplitude modulation (QAM) is a highly bandwidth efficient transmission technique for digital communications. It makes use of multiple signal phase and amplitude levels to carry multiple bits per symbol. This requires accurate and robust carrier phase and frequency estimation in the receiver. / Thesis (PhDElectronicEngineering)--University of South Australia, 2002

<p>Class D amplifiers are becoming increasingly popular in audio devices. The strongest reason is the high efficiency which makes it advantageous for portable battery-driven products.</p><p>Infineon Technologies is developing products in this area, and has recently filed a patent application regarding an implementation of a part of the class D amplifier. The aim of this Master’s thesis is to evaluate a digital open-loop implementation of a class D amplifier, using the pending patent solution, and discuss the differences from an analog closed-loop implementation.</p><p>The focus has been on generating a high resolution PWM signal with a relatively low clock frequency. To achieve this, a hybrid of a counter and a self-calibrating tapped delay-line are used as a pulse generator. A model of the pulse generator was developed which made it possible to study how sampling frequency and different types of quantization affected quality parameters such as THD and SNR. With the results from the model two systems were implemented and simulated in HDL and as circuit schematics.</p><p>The proposed digital open-loop class D amplifier was found to be useful in voice-band applications and for music. Since the open-loop structure suffers from poor rejection of power supply ripple, either error correction or a regulated power supply is needed. If much effort is put on the different parts of the amplifier the result can be really good but, depending on other constraints on the system, it may be simpler and less time consuming to use the analog circuit with feedback to achieve hi-fi quality.</p><p>In summary, the combination of a counter and a self-calibrating tapped delay-line as a pulse generator is very useful in high resolution low-power systems. To avoid errors the delay-line and calibration can be made very accurate but with the expense of higher power consumption and area. However, the technique benefits from the small and fast logic devices available in deep sub-micron process technologies, which may finally lead to an advantage in power consumption and cost over the closed-loop analog solution.</p>

Class D amplifiers are becoming increasingly popular in audio devices. The strongest reason is the high efficiency which makes it advantageous for portable battery-driven products. Infineon Technologies is developing products in this area, and has recently filed a patent application regarding an implementation of a part of the class D amplifier. The aim of this Master’s thesis is to evaluate a digital open-loop implementation of a class D amplifier, using the pending patent solution, and discuss the differences from an analog closed-loop implementation. The focus has been on generating a high resolution PWM signal with a relatively low clock frequency. To achieve this, a hybrid of a counter and a self-calibrating tapped delay-line are used as a pulse generator. A model of the pulse generator was developed which made it possible to study how sampling frequency and different types of quantization affected quality parameters such as THD and SNR. With the results from the model two systems were implemented and simulated in HDL and as circuit schematics. The proposed digital open-loop class D amplifier was found to be useful in voice-band applications and for music. Since the open-loop structure suffers from poor rejection of power supply ripple, either error correction or a regulated power supply is needed. If much effort is put on the different parts of the amplifier the result can be really good but, depending on other constraints on the system, it may be simpler and less time consuming to use the analog circuit with feedback to achieve hi-fi quality. In summary, the combination of a counter and a self-calibrating tapped delay-line as a pulse generator is very useful in high resolution low-power systems. To avoid errors the delay-line and calibration can be made very accurate but with the expense of higher power consumption and area. However, the technique benefits from the small and fast logic devices available in deep sub-micron process technologies, which may finally lead to an advantage in power consumption and cost over the closed-loop analog solution.

This dissertation presents a study of linearization techniques that have been applied to power amplifiers in the cellular communication industry. The objective of this work is to understand the limitations of power amplifiers, specifically the limitations introduced by the use of spectrally efficient modulation schemes. The digitization of communication systems has favored the use of new techniques and technologies capable of increasing the efficiency of costly power amplifiers. The work explores traditional and digital linearization systems; an algorithm based on the principles of natural recombination is proposed to directly address the limitations of previous embodiments. Previous techniques, although effective, have significant implementation costs that increase exponentially with the increasing signal bandwidths. The proposed software-hardware architecture significantly reduces implementation costs and the overall complexity of the design without sacrificing performance. To fulfill the requirements of this study, multiple systems are implemented through simulation and closed-loop hardware. Both simulation and hardware embodiments meet the expected performance metrics, providing validation of the proposed algorithm. The application of the algorithm to memory power amplifier linearization is a new approach to adaptive digital pre-distortion using narrowband feedback. The work will show performance improvements on an amplifier with memory effects suggesting that this technique can be employed as a lower-cost solution to meet requirements when compared to typical system implementations.

Quadrature amplitude modulation (QAM) is a highly bandwidth efficient transmission technique for digital communications. It makes use of multiple signal phase and amplitude levels to carry multiple bits per symbol. This requires accurate and robust carrier phase and frequency estimation in the receiver. / Thesis (PhDElectronicEngineering)--University of South Australia, 2002.

Quadrature amplitude modulation (QAM) is a highly bandwidth efficient transmission technique for digital communications. It makes use of multiple signal phase and amplitude levels to carry multiple bits per symbol. This requires accurate and robust carrier phase and frequency estimation in the receiver. / Thesis (PhDElectronicEngineering)--University of South Australia, 2002

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 146-148). Also available in electronic format on the Internet.

Thesis (M. Eng.)--Carleton University, 2001. / Includes bibliographical references (p. 72-74). Also available in electronic format on the Internet.