High resolution multi-bit sigma-delta modulator architecture

The fundamental difficulty with traditional multi-bit sigma-delta converters is the requirement for a highly accurate DAC in the feedback path. To avoid this constraint, we start by considering a basic multi-bit topology with single-bit feedback and then extend it to achieve high resolution at wide bandwidth. This topology is accomplished by extracting the coarse single-bit error and pipelining it through multi-bit quantization with filtering and feedback. The coarse single-bit error is then exchanged for the finer multi-bit error at the output by appropriate digital filtering and error cancellation