Delta-sigma modulator with non-uniform quantization

In this paper, a novel delta-sigma modulator which has a non-uniform quantizer is proposed. The step sizes of a non-uniform quantizer are, in general, uniquely determined by the probability density function (PDF) of an input signal amplitude, while delta-sigma modulators usually become unstable when the non-uniform quantizer is directly applied to them. It is found that the proposed delta-sigma modulator reduces a quantization noise and works in a stable condition. To guarantee the stability of the delta-sigma modulator, the maximum output value of the quantizer is fixed at a certain value. The rest of the output and threshold values of the non-uniform quantizer are determined by the PDF of the input signal amplitude. The simulation results show that the quantization noise power is reduced by up to 2.90 dB when the non-uniform quantizer is applied.