Sigma delta modulators using semi-uniform quantizers

A semi-uniform quantizer for multi-bit sigma delta modulator is proposed. It has smaller quantization steps for smaller inputs and vice versa. The use of a k-bit semi-uniform quantizer achieves roughly the same performance as using a (k+1)-bit uniform quantizer over main part of the input signal dynamic range. The semi-uniform quantizer can easily be constructed in the same way as constructing a uniform quantizer