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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Author: search.filters.author.Chang, THSubject: search.filters.subject.analog-to-digital converters (ADCs)

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    Dynamic range improvement of multistage multibit Sigma Delta modulator for low oversampling ratios
    (2005-02-01)
    Chang, TH
    ;
    Dung, LR
    ;
    電控工程研究所
    ;
    Institute of Electrical and Control Engineering
    This paper presents an improved architecture of the multistage multibit sigma-delta modulators (EAMs) for wide-band applications. Our approach is based on two resonator topologies, high-Q cascade-of-resonator-with-feedforward (HQCRFF) and low-Q cascade-of-integrator-with-feedforward (LQCEFF). Because of in-band zeros introduced by internal loop filters, the proposed architecture enhances the suppression of the in-band quantization noise at a low OSR. The HQCRFF-based modulator with single-bit quantizer has two modes of operation, modulation and oscillation. When the HQCRFF-based modulator is operating in oscillation mode, the feedback path from the quantizer output to the input summing node is disabled and hence the modulator output is free of the quantization noise terms. Although operating in oscillation mode is not allowed for single-stage SigmaDeltaM, the oscillation of HQCRFF-based modulator can improve dynamic range (DR) of the multistage (MASH) SigmaDeltaM. The key to improving DR is to use HQCRFF-based modulator in the first stage and have the first stage oscillated. When the first stage oscillates, the coarse quantization noise vanishes and hence circuit nonidealities, such as finite op-amp gain and capacitor mismatching, do not cause leakage quantization noise problem. According to theoretical and numerical analysis, the proposed MASH architecture can inherently have wide DR without using additional calibration techniques.