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当Sigma_Delta调制器的前向通道积分器个数为L时 ,称该调制器为Sigma_Delta调制器。本文首先给出了Sigma_Delta调制器的线性模型。根据该线性模型 ,并考虑输入噪声的影响 ,将L阶调制器设计分解为线性滤波网络和非线性量化器的设计。这样 ,既保证了系统的稳定 ,又使基带内的量化噪声减至最小 ,获得了最佳的量化噪声整形 ,将原来在整个频带内均匀分布的白噪声推向了高频端。设计了噪声传递函数NTF ,并对其进行了优化。最后 ,给出了 5阶Sigma_Delta调制器的仿真结果。仿真结果表明 ,调制器的分辨率主要由噪声传递函数NTF的零极点分布特性决定 ,本文提出的设计方法是可行的。仿真数据对调制器的设计具有重大意义。
When the Sigma_Delta modulator has a forward channel integrator of L, the modulator is called a Sigma_Delta modulator. This article first gives a linear model of the Sigma_Delta modulator. According to the linear model and considering the influence of input noise, the L-order modulator design is decomposed into the design of linear filter network and non-linear quantizer. In this way, not only the stability of the system is ensured, but also the quantization noise in the baseband is minimized, the best quantization noise shaping is obtained, and the white noise originally distributed uniformly in the whole frequency band is pushed to the high frequency end. The noise transfer function NTF is designed and optimized. Finally, the simulation results of the 5th order Sigma_Delta modulator are given. The simulation results show that the resolution of the modulator is mainly determined by the zero-pole distribution of the noise transfer function NTF. The design method proposed in this paper is feasible. The simulation data is of great significance to the design of the modulator.