Delta-sigma data converters for broadband digital communications.
Published: 2004
Language: eng
Number of pages: 318
Description: Accordingly, to meet the stringent ADC specifications imposed by emerging broadband communication applications, this thesis explores the following: (1) High-Speed High-Resolution Delta-Sigma (DeltaSigma)  ADCs: Oversampling DeltaSigma ADCs can achieve a high-resolution data conversion in low-speed applications using low-accuracy analog components. However, extending these ADCs to high-speed applications requires lowering the oversampling ratio (OSR), due to both power and CMOS technology limitations. Unfortunately, this significantly limits the efficiency of a DeltaSigma ADC in achieving a high-resolution analog/digital (A/D) conversion. Therefore, this thesis presents several techniques to enable the OSR lowering in high-speed DeltaSigma ADCs without compromising the resolution. Specifically, a low-distortion single-stage architecture is proposed for high-order multibit DeltaSigma modulators. Furthermore, a dynamic-element-matching (DEM) technique, called Pseudo Data-Weighted-Averaging (Pseudo DWA), with reduced tone behavior at a low OSR is proposed for the linearization of the digital-to-analog converter (DAC) in a multibit DeltaSigma modulator. (2) Low-Voltage Switched-Capacitor ( SC) Circuit Implementation: To demonstrate the practicality of the proposed modulator architecture and DAC-linearization technique when the OSR and the supply voltage are limited by the technology, a DeltaSigma modulator prototype is designed using SC circuit techniques and fabricated in a 0.18-mum standard digital CMOS process. When operated from a 1.8-V supply, it achieves a 13-bit spurious-free dynamic range (SFDR) and a 12-bit signal-to-noise ratio (SNR) over a 3-MS/s conversion bandwidth with a 1.85-V pp input-signal range. The analog and digital power consumptions are, respectively, 32.4 mW and 12.6 mW. The on-chip references dissipate 14.4 mW. Accordingly, this DeltaSigma modulator was one of the few early-reported CMOS DeltaSigma modulators targeting high-speed (&ge;2 MS/s) high-resolution (&ge;12 bits) applications and operating from a low supply voltage (&le;1.8 V). Furthermore, its measured performance compared favourably to the previously-reported state-of-the-art DeltaSigma modulators.Ironically, the significance of analog integrated-circuit design is growing more prominent in today's "digital" communication age due, in part, to data converters. Specifically, the proliferation of broadband digital communication applications is stimulating the evolving research towards the development of analog-to-digital converters (ADCs) with higher speeds and higher resolutions. These ADCs must be implemented in standard digital CMOS processes for higher system integration and lower fabrication costs. However, in nano-scale CMOS technologies, the decreasing supply voltages and the shrinking devices with poor analog-processing capabilities complicate the low-power design of high-resolution analog circuits.
Notes: Adviser:  Ken Martin.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 00-00, Section: B, page: 5304.