Digitally controlled "programmable" active filters

Abstract

In this research a general purpose digitally controlled analog filter is presented. The novel design is a cascade of second order sections that are individually programmed to achieve any filtering topologies. Two-binary words are used to control the pole frequency co p and selectivity Qp of each section independently. Each second-order section is a Generalized-Immittance Converter (GIC) biquads which are known for their high stability and low active and passive sensitivity. CMOS switches are used to electronically relocate the minimum number of passive elements to achieve function programmability. Switches are also used to select the number of cascaded sections to realize higher order transfer functions.