On the inherent harmonic distortion of first-order Σ-Δ modulators

Sigma-delta (Σ-Δ) modulators are used as a robust means of providing high-linearity analog-digital and digital-analog conversion. For first-order Σ-Δ modulators, idle channel conditions which produce colored quantization noise have been considered the only inherent limitation where, even for highly periodic inputs, harmonic distortion dominates the quantizer error in the output of first-order Σ-Δ modulators. This places an inherent limit on the achievable performance of such devices, irrespective of the state-of-the-art in implementation.