Behavioral Modeling Methods for Switched-Capacitor $\Sigma \Delta$ Modulators
Behavioral Modeling Methods for Switched-Capacitor $\Sigma \Delta$ Modulators
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DOI：
10.1109/tcsi.2007.897767
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发表时间：
2007-06
期刊：
影响因子：
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通讯作者：
G. Suárez;M. Jimenez;F. Fernández
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文献类型：
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作者：
G. Suárez;M. Jimenez;F. Fernández
Sigma-delta调制器（SigmaDeltaMs）是过采样模数转换器和数模转换器（DAC）的基础元件。虽然晶体管级模拟是已知的这些元件最精确的方法，但由于其长时间的计算要求，这种方法对于复杂系统变得不切实际。行为建模已经成为解决这一问题的可行方法。本文研究了低功耗、高速SigmaDeltaMs精确建模的风格和问题，并介绍了两种新的开关电容（SC）积分器的行为模型。第一个模型基于SC积分器的瞬态响应，包括放大器跨导、输出电导和动态容性负载对稳定时间的影响。第二个模型是基于系统的符号节点导纳矩阵表示。抖动、热噪声和DAC失配等非理想性也得到了解决，并包含在具有单个电平平均的双频、GSM/WCDMA、二阶、多位SigmaDeltaM模型中。采用VHDL-AMS和MATLAB Simulink作为建模语言。两种模型都通过实验数据进行了验证，在信噪比和失真率方面显示出竞争性的结果。将该模型与传统模型进行了比较分析，重点讨论了积分器动力学的退化效应。此外，还对所提模型的一般仿真速度进行了分析。
Sigma-delta Modulators (SigmaDeltaMs) are cornerstone elements in oversampled analog-to-digital converters and digital-to-analog converters (DAC). Although transistor-level simulation is the most accurate approach known for these components, this method becomes impractical for complex systems due to its long computational time requirements. Behavioral modeling has become a viable solution to this problem. In this paper, we study styles and issues in the accurate modeling of low-power, high-speed SigmaDeltaMs and introduce two new behavioral models for switched-capacitor (SC) integrators. The first model is based on the SC integrator transient response, including the effects of the amplifier transconductance, output conductance, and the dynamic capacitive loading effect on the settling time. The second model is based on a symbolic node admittance matrix representation of the system. Nonidealities such as jitter, thermal noise, and DAC mismatch are also addressed and included in a dual-band, GSM/WCDMA, second-order, multibit SigmaDeltaM model with individual level averaging. VHDL-AMS and MATLAB Simulink were used as modeling languages. Both models are validated against experimental data, showing competitive results in the signal-to-noise-plus-distortion ratio. A comparative analysis between the proposed and a traditional model is presented, with emphasis on the degrading effects due to the integrator dynamics. Moreover, a general simulation speed analysis of the proposed models is addressed.