Delta-sigma modulators employing continuous-time circuits and mismatch-shaped DACs

approved: Richard Schreier Delta-sigma modulators are currently a very popular technique for making highresolution analog-to-digital and digital-to-analog converters. 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. Though the initial uses of deltasigma modulators were in the audio field, the development of bandpass modulators opened up the application range to radar systems, digital communication systems and instruments which convert IF, or even RF, analog signals directly to digital form. This thesis presents a method used to analyze and synthesize continuous-time delta-sigma modulators for given specifications. A fourth-order prototype continuous-time bandpass delta-sigma modulator employing gm-LC resonator structure is demonstrated on a PCB board and measurement results corroborate the theory. To allow the construction of very high performance delta-sigma modulators, this thesis presents an architecture for a multibit DAC constructed from unit elements which shapes element mismatches. Theoretical analysis and simulation shows that this architecture greatly increases the noise attenuation in the band-of-interest and facilitates the use of multibit quantization in delta-sigma modulators. The methods presented in this thesis will allow high-frequency wideband bandpass delta-sigma modulators to be constructed. Redacted for Privacy Redacted for Privacy Delta-Sigma Modulators Employing Continuous-lime Circuits and Mismatch-Shaped DACs by Bo Zhang A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Completed April 3, 1996 Commencement June 1996 ©Copyright by Bo Zhang April 3, 1996 All Rights Reserved Doctor of Philosophy thesis of Bo Zhamz presented on April 3, 1996

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