Oversampled multi-bit sigma-delta A/D converters

The objective of this research is geared towards proposing sigma-delta modulators that will achieve high resolution at wide bandwidths, meaning A/D conversion at rates exceeding 1 MHz with a resolution of at least 12 bits [1, p.219]. As will become clear later, this task not only requires the use of high-order noise shaping but also multi-bit quantization. On that basis, this thesis starts with a basic sigma-delta topology which employs multi-bit quantization with single-bit feedback thus avoiding the very strict linearity requirements imposed on DAC in the feedback path of a sigma-delta loop. The concept is then further extended to develop novel sigma-delta topologies that accomplish a synergetic combination of the advantages of sigma-delta and pipeline ADCs to provide wide dynamic range at wide bandwidths, a performance which may not be currently realized using either of the structures alone. The validity of the proposed topologies is confirmed by system level simulations.