High-order vector sigma-delta modulators

Abstract

An attractive technique, useful for the implementation of multibit sigma-delta (/spl Sigma//spl Delta/) converters, is the spectral shaping of the unknown errors introduced by the analog circuitry of the digital-to-analog conversion (DAC). This is achieved by encoding the multibit /spl Sigma//spl Delta/ sequence of the modulator output to an array of single-bit /spl Sigma//spl Delta/ sequences. In this paper, it is shown how a multibit /spl Sigma//spl Delta/ converter can be implemented directly using an array of M joint single-bit /spl Sigma//spl Delta/ modulators, the vector /spl Sigma//spl Delta/ modulator (V/spl Sigma//spl Delta/M). A model for stability and performance analysis of high-order V/spl Sigma//spl Delta/M is proposed. It is shown how the structure of the V/spl Sigma//spl Delta/M is modified in order to encode a PCM signal to an array of single-bit /spl Sigma//spl Delta/ sequences. Simulations are carried out in order to show the successful operation of high-order V/spl Sigma//spl Delta/M's, and check the validity of the proposed model.