开关电容椭圆低通滤波器的设计与仿真

本文结合八阶椭圆低通滤波器的设计，讨论了开关电容滤波器计算机辅助设计的一种有效方法。将开关电容网络的时变拓扑，变换为时不变拓扑，建立开关电容模拟电阻的Z域模型，与电容、运算放大器模型结合，构成二阶开关电容椭圆滤波器。将二阶开关电容滤波器级联，给出了八阶开关电容椭圆低通滤波器的设计与PSPICE仿真程序。仿真输出曲线显示了椭圆低通滤波器的陡峭衰减特性和理想幅频特性，符合设计要求。适用于高通、带通、陷波等各种滤波器的设计与仿真。

Design and Simulation for Switched Capacitor Elliptic Low Pass Filters

Combining with the design of 8th-order elliptic lowpass filter, a valid computer- aided method to design switched capacitor filters is discussed in this paper. After the switched capacitor network is transformed from time-varying topology into timeinvariant topology and z-domain models of equivalent resistance using switched capacitor is obtained, a 2nd-order switched capacitor ellipse filter can be realized by assembling z-domain model, capacitor and operational amplifier models. Cascading the 2nd-order switched capacitor filters, the design of 8th-order switched capacitor for ellipse lowpass fiher and its PSPICE simulation program have been given. The simulation resuits show steep attenuation and perfect transfer characteristics of ellipse lowpass filter, which are satisfied with the design specifications. The proposal can be used for designing and simulating highpass, bandpass, bandreject and other filter circuits.