Design of semi-uniform quantizers and their application in sigma delta A/D converters

• 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 mum CMOS process. At 32 x 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.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Datorsystem (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Computer Systems (hsv//eng)

Nyckelord

sigma

delta

quantization

modulation

OTA

adc

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