一种用于ADSL的高精度调制器的建模与仿真

Behavior Modeling and Simulation of a High Resolution Modulator for ADSL applications

要模数转换问题的研究中,介绍了∑-△调制器的过采样和噪声整形技术,为提高转换精度和速率,提出了一个采用四阶级联结构和∑-△调制技术实现高精度的调制器的行为级模型,根据影响建模的各种非理想因素,对各种实际非理想因素(例如开关热噪声、时钟抖动、运放的有限直流增益等)通过优化系统参数之后,可以得到一个用于ADSL设计中的高精度∑-△调制器行为级模型。并在MATLAB下对其仿真验证,结果表明为实际设计提供了依据。调制器在基带带宽1.5MHz、24倍过采样率条件下,系统的信噪比达到87dB,精确度可达14比特。

This paper presents overshanping and noise - shanging techniques used in sigma - delta modulator. Behavior modeling and simulation of a high resolution Sigma - Delta modulator by using 4 - rd Cascade and sigma - delta modulator technique for ADSL applications is presented. Analyzed the main non - ideal mechanisms affecting the performance of Sigma- Delta modulator （such as switch thermal noise, clock jitter, finite dc gain of OPA, etc）and opti- mized the coefficients of the system by using MATLAB SIMULINK. In condition of various actual non - ideal performance of Sigma - Delta, simulation results show that the modulator system can achieve a SNR higher than 87dB and 14 bits accuracy with an overshaping ratio of 24.