Method to Convert Analog Filters to Digital Filters

The analog filters are usually converted to IIR digital filters using appropriate transformation of system function from s-domain to z-domain. Recently another approach of converting an analog filter described by a diagram or a netlist to a digital filter has been proposed. Using this Analog Filter Netlist to Digital Filter Statements (AFN-DFS) approach, one can use a previous implementation in analog domain and a software code for the digital filter may be available rapidly. In this paper, we present a state-space (SS) based approach that provides an automatic procedure to convert an analog filter described by a diagram or a netlist to a digital filter described in system function form. The procedure consists of three main parts: first the state-space of the analog filter is computed based on diagram or netlist of the analog circuit, then a conversion from analog domain to digital domain is used. Finally the digital filter is delivered in system function form.