Higher-order DWA in bandpass delta-sigma modulators and its implementation

Abstract

This paper proposes a simple implementation of a higher-order data weighted averaging algorithm to spectrally shape mismatch errors of a multi-bit D/A converter in a bandpass (BP) delta-sigma modulator. The proposed implementation avoids the need for a complex and slow sorting function that is usually associated with a higher-order DWA algorithm. An algorithm based on updating two pointers is used, similar as the widely used first-order DWA algorithm. The implementation is based on a pulse density modulated DAC that is clocked at a 3x higher rate compared to the delta-sigma modulator clock to accurately implement the 1x and 3x weight factors that are required by the algorithm. The implementation can also be used in a generalized bandpass DWA algorithm that can be easily adjusted to tune the noise-shaping characteristic to different center frequencies.