Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 76-78). Also available on the World Wide Web.

Delta-sigma modulators are currently a very popular technique for making high-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). These oversampled data converters have several advantages over conventional Nyquist-rate converters, including an insensitivity to many analog component imperfections, a simpler antialiasing filter and reduced accuracy requirements in the sample and hold. A recent development in the realm of delta-sigma-based ADC and DAC systems is the use of multilevel (as opposed to binary) quantization. This development owes its existence to the discovery of a variety of techniques which cause linearity errors of the embedded multilevel DAC to be attenuated in the frequency band of interest. This thesis presents several methods for shaping the DAC element mismatch error and reducing the dynamic error in the band of interest. To demonstrate the effectiveness of the proposed algorithms, a current-mode unit element DAC is designed and used as a test bed. Both theoretical analysis and experimental results show that these methods can greatly attenuate the noise in the band of interest. The methods presented in this thesis will allow high performance, high-frequency wideband delta-sigma modulators to be constructed. / Graduation date: 1998

This dissertation investigates the constraints which arise when switched-capacitor (SC) delta-sigma modulators are designed for low-voltage operation, targeting also low power dissipation, and proposes methods of improving the performance and optimizing for low power dissipation. This is accomplished by identifying critical elements whose performance can lead to increased power dissipation, as well as the fundamental limitations of available analog circuit techniques. A prototype was designed and fabricated, which reflected these findings, and therefore exhibited good performance and nearly optimum power dissipation. One of the key performance parameters is the dc gain of the amplifier in the first stage; it should be high. This is necessary for high linearity and low quantization noise leakage. In low-voltage operation, it may become impractical to use conventional topologies employing cascoding techniques (e.g., folded-cascode) which provide high gain in one single stage. Rather, cascaded structures have to be used. The disadvantage of the latter is the necessity for frequency compensation which results in increased power dissipation. Hence, another objective of this work is to exploit techniques which compensate for the open-loop gain characteristic of the amplifier (dc gain and nonlinearity), thus permitting the utilization of single-stage low-gain topologies. Predictive correlated double sampling is one of such techniques and is analyzed in detail. / Graduation date: 1998

Graduation date: 1994

Coplanar microstrip structures placed on dielectric substrates are used as high frequency electro-optic modulators. The method of lines, a mathematical technique for solving partial differential equations, has been applied to solve for the propagation characteristics of such a configuration. It has been determined that simple transmission line models are adequate to describe this system. The propagation characteristics are expressed in terms of the equivalent impedance and the phase velocity of the signal on the microstrip. In order to maximize the effective bandwidth of the modulator, the impedance is matched to that of the surrounding dielectric substrate, and the difference in the phase velocities of the two signals is minimized. The numerical technique developed here allows for the analysis of inhomogeneous dielectric substrates, so that trench structures for tuning the propagation characteristics to their desired values can be modelled. The numerical results for typical structures are presented, and suggest that the method of lines is a viable one for analyzing these modulator structures. / Graduation date: 1991

Graduation date: 1993

University of Macau / Faculty of Science and Technology / Department of Electrical and Electronics Engineering

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

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