Adaptive high performance ΣΔ modulator designs

In this paper, different solutions to the saturation problem of the integrator building block of sigma-delta (SD) modulators are proposed. Saturation causes an error that limits the dynamic input range of SD A/D converters and consequently decreases its SNR. The proposed structure, using a variable gain integrator followed by a non-uniform quantizer as companding, makes the usage of higher input levels to the A/D converter possible. Also with speech signals in which very high and very low signals reside, this architecture performs much better.