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 time-invariant 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 filter and its PSPICE simulation program have been given.The simulation results 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.