Implementation of Active Filters for Speech Processing using Switched-Capacitors

Abstract

The main objective of this paper is to design and implement a Chebyshev band pass filter using a switched-capacitor realization. The transfer function is to be realized as the product of a second-order high-pass filter in cascade with second-order low-pass filter. Switched capacitor filters are normally used in an integrated circuit product environment as resistors, are expensive and not easily controlled. Switched capacitors may be used to simulate resistors to an acceptable degree of accuracy using capacitors and MOSFETs, and are generally less costly than resistors.  The switching functions of the MOSFETs produce a discrete response rather than a continuous response from the filter.  Therefore, Z Transforms are employed rather than S Transforms, and just as in digital filters, aliasing effects occur.  Any Z Transform approximation to a continuous function may be used to design a switched capacitor filter. The design and implementation is done using Mentor Graphics EDA tool in TSMC 180nm technology.