Non-linear deterministic dithering of sigma-delta modulators

Sigma-delta modulators suffer from idle tone artefacts which degrade their linearity, even with high order modulation. The conventional linearization technique is to dither the quantizer with an external random noise source. Although successful, dither can be inefficient to implement and does not take advantage of certain properties of the one-bit quantizer. It has been shown that relatively linear modulator performance is inherently possible without the need for an external noise source, by modifying the quantizer operation with a nonlinear technique called bit-flipping. Two bit-dipping algorithms have been described, which enhance the linearity of the modulator. It has been shown that it is possible to linearize the modulator and reduce the quantization error power in the baseband, at the expense of increased hardware complexity. Both techniques are straightforward to implement and optimal performance is obtained by the choice of a single constant