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17th International Conference on VLSI Design   p. 151
An Element Rotation Algorithm for Multi-bit DAC Nonlinearities in Complex Bandpass \Delta\SigmaAD Modulators
Hao San, Gunma University, Japan
Haruo Kobayashi, Gunma University, Japan
Shinya Kawakami, Gunma University, Japan
Nobuyuki kuroiwa, Gunma University, Japan

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DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/ICVD.2004.1260917
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Abstract
This paper presents a technique for improving the resolution of complex bandpass \Delta\SigmaADCs which are used for wireless communication systems. Oversampling and noise-shaping are used to achieve high accuracy of a \Delta\SigmaAD modulator. However when a multi-bit DAC is used inside a modulator, nonlinearities of the DAC are not noise-shaped and the SNR of the \Delta\SigmaADC degrades. For the conversion of complex intermediate frequency (IF) input signals, a complex bandpass \Delta\SigmaAD modulator can provide superior performance to a pair of real bandpass \Delta\SigmaAD modulators of the same order. This paper proposes a new noise-shaping algorithm - implemented by adding simple digital circuitry - to reduce the effects of nonlinearities in multi-bit DACs of complex bandpass \Delta\SigmaAD modulators. We have performed simulation with MATLAB to verify the effectiveness of the algorithm, and the results show that the proposed algorithm can improve the SNR of a complex bandpass \Delta\SigmaADC with nonlinear internal multi-bit DACs.
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Citation:  Hao San, Haruo Kobayashi, Shinya Kawakami, Nobuyuki kuroiwa, "An Element Rotation Algorithm for Multi-bit DAC Nonlinearities in Complex Bandpass \Delta\SigmaAD Modulators," vlsid, p. 151,  17th International Conference on VLSI Design,  2004