An improved technique for reducing baseband tones in sigma-delta modulators employing data weighted averaging algorithm without adding dither

Author

Chen, Kuan-Dar ; Kuo, Tai-Haur

Author_Institution

Dept. of Electr. Eng., Nat. Cheng Kung Univ., Tainan, Taiwan

Volume

46

Issue

1

fYear

1999

fDate

1/1/1999 12:00:00 AM

Firstpage

63

Lastpage

68

Abstract

The data weighted averaging (DWA) algorithm used in multibit sigma-delta modulators (SDM) is troubled by baseband tones resulting from component mismatch of the SDM´s internal multi-bit digital-to-analog converter (DAC). In this paper, we analyze DAC baseband tones and find them closely correlated to the number of unit elements used in the DAC. An improved technique is proposed for shifting the DAC tones away from the baseband without adding dither. For third-order sigma-delta modulators with an oversampling ratio (OSR) of 64 and either a nine-level or eight-level internal DAC with 0.5%-2% random component mismatches, simulation reveals that the DWA algorithm with the proposed technique can achieve nearly perfect first-order DAC noise shaping in the baseband and, on the average, 12 dB improved signal-to-(noise and distortion) ratio and 20 dB improved in-band distortion

Keywords

Monte Carlo methods; circuit noise; interference suppression; sigma-delta modulation; signal sampling; switched capacitor networks; ADC; SNDR; baseband tones reduction; component mismatch; data weighted averaging algorithm; digital-to-analog converter; dither; first-order DAC noise shaping; internal multi-bit DAC; sigma-delta modulators; Attenuation; Baseband; Capacitors; Delta-sigma modulation; Digital modulation; Distortion; Linearity; Multi-stage noise shaping; Noise shaping; Signal processing algorithms;

fLanguage

English

Journal_Title

Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on

Publisher

ieee

ISSN

1057-7130

Type

jour

DOI

10.1109/82.749090

Filename

749090