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开关电容滤波器(Switched-capacitor filter简称SCF)是国外近几年出现的一种全集成化有源滤波器。它具有精度高、灵敏度低等一系列优点。本文将重点讨论如何运用无损离散积分器(Loss-Less Discrete Integrator简称LDI)映射变换来实现开关电容滤波。 为了进行优化计算,文中避免运用Mason公式的烦琐推导,将按本文给出的规律,直接写出这种SCF的设计公式。按此公式,采用系数匹配法优化原理和牛顿法,可消除运用LDI映射实现SCF所导致的误差。 本文给出了SCF优化设计全过程的具体步骤和算例。 按本文给出的优化设计方法,在满足滤波设计要求的前提下,可使SCF的通带截止频率接近开关频率的二分之一。
Switched-capacitor filter (referred to as SCF) is a fully integrated active filter in recent years abroad. It has a high precision, low sensitivity and a series of advantages. This article will focus on how to use the lossless discrete integrator (Loss-Less Discrete Integrator referred to as LDI) mapping transformation to achieve switched capacitor filtering. In order to optimize the calculation, the paper avoids cumbersome derivation of the Mason formula, and will directly write the design formula of this SCF according to the law given in this article. According to this formula, using the coefficient matching method to optimize the principle and the Newton method can eliminate the error caused by using the LDI mapping to achieve SCF. This paper gives the specific steps and examples of the whole process of SCF optimization design. According to the optimization design method given in this article, the cut-off frequency of the passband of SCF can be close to one half of the switching frequency under the premise of meeting the filter design requirements.