Cascaded noise-shaping modulators for oversampled data conversion

In oversampled data converters, sampling at well above the Nyquist rate is combined with feedback and digital filtering to exchange resolution in time for that in amplitude. By this means it is possible to aggressively exploit the scaling of VLSI technology to increase the precision with which analog signals can be digitized. As a consequence, oversampling now plays a dominant role in the implementation of high-resolution A/D and D/A converters for applications such as digital audio. Moreover, this approach is being extended to digitizing signals with bandwidths as high as several MHz through architectural and circuit innovations that enable operation at relatively low oversampling ratios. This paper outlines the principle of noise-shaping modulators for both A/D and D/A conversion.