Comparison of Two Bandpass Delta - Sigma A / D Converter Architectures

This study compares the performance and robustness of single loop and cascaded bandpass delta-sigma analog-to-digital (A/D) converter architectures. A 4 order single loop modulator and a 4 order 1-1 cascaded architecture are designed to provide a basis for comparison of SNR performance and robustness to capacitor mismatch and finite operational amplifier gain variations. Several different approaches to the design of error cancellation circuitry in the cascaded architecture are presented. MATLAB simulations of the two architectures is used to show that the single loop modulator yields better SNR performance than the cascaded modulator. Both architectures perform comparably under capacitor mismatch variations. The effects of operational amplifier gain on both architectures are insignificant for gains greater than about 8,000. Thesis Supervisor: Charles G. Sodini Title: Professor of Electrical Engineering and Computer Science ACKNOWLEDGEMENTS I would like to first and foremost, thank my mother, Nazmiye, for all her love, affection, and help that she has selflessly given to me throughout my whole life. My friend through both thick and thin, my teacher of both technical matters and life, without her support nothing I have ever accomplished in my life would have been possible. I would also like to thank my Thesis Advisor, Professor Charlie Sodini, my Academic Advisor, Bernard Lesieutre, and my Technical Supervisors at Draper Laboratory, Paul Ward and Ed Balboni, for their technical support and guidance through out my work on this project. I am also grateful to the staff at Draper who made working there enjoyable, and in particular, to Ralph Haley and Ochida Martinez, who never failed to listen and offer supporting words. Finally, I would like to thank my friends in general who made studying at MIT bearable and at times very enjoyable. In particular, I would like to thank Keith Santarelli, Louis Nervegna, and Phil Juang for their support, encouragement, and the many laughs during stressful times, both during my thesis work as well as during classes. Knowledge should mean a full grasp of knowledge; Don't boast of reading, mastering science Knowledge means to know yourself, heart and soul. Or of all your prayers and obeisance. If you have failed to understand yourself, If you know not who God is Then all of your reading has missed its call All of your learning is of no use at all. What is the purpose of reading those books? Yunus Emre says to you, pharisee, So that Man can know the All-Powerful. Make the holy pilgrimage if need be If you have read, but failed to understand, A thousand times but if you ask me, Then your efforts are just a barren toil The visit to a heart is best of all. Yunus Emre (13"' Century Turkish Poet) This thesis was prepared at The Charles Stark Draper Laboratory, Inc, under Internal Company Sponsored Research No. C312. Publication of this thesis does not constitute approval by Draper or the sponsoring agency of the findings or conclusions herein. It is published for the exchange and stimulation of ideas. Permission is hereby granted by the Author to the Massachusetts Institute of Technology to reproduce any or all of this thesis.