Abstract
In this paper a new type of non-uniform quantizer, semi-uniform quantizer, is introduced. A k-bit semi-uniform quantizer uses the thresholds defined by a (k + 1)-bit uniform quantizer and arranges them in such a way that small-amplitude inputs will be quantized by small quantization steps and large-amplitude inputs by large quantization steps. Therefore the total quantization error power could be reduced and the modulator's dynamic range could be increased by 1-bit. The condition for a semi-uniform quantizer to achieve a better performance than a uniform quantizer is analyzed and verified using a second order 3-bit sigma delta modulator prototype chip, fabricated in 0.35 μm CMOS process. At 32× oversampling ratio the modulator achieves 81 dB dynamic range and 63.8 dB peak SNDR with 3-bit semi-uniform quantizer. With 3-bit uniform quantizer the dynamic range is 70 dB and the peak SNDR is 54.1 dB.
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Li, B., Tenhunen, H. Design of Semi-Uniform Quantizers and Their Application in Sigma Delta A/D Converters. Analog Integrated Circuits and Signal Processing 41, 253–267 (2004). https://doi.org/10.1023/B:ALOG.0000041640.63105.2d
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DOI: https://doi.org/10.1023/B:ALOG.0000041640.63105.2d