Adaptive IIR filtering of delta-sigma modulated signals

A novel method for constructing adaptive recursive digital filters is presented. The proposed filters operate at the oversampled rate directly on the bitstream produced by delta-sigma analog-to-digital converters. Thus, these filters obviate the need for the decimation and interpolation circuitry required by Nyquist-rate filters. In addition, these adaptive filters-based on a variant of the familiar LMS (least mean square) algorithm-utilize only simple hardware components such as adders and registers, making the scheme hardware-efficient and a viable alternative to conventional, Nyquist-rate LMS adaptive filters.<>