Searching for TAC filter structures using rule-based system

A rule-based methodology is presented to search for graphs describing structures of circuits with given transfer function. TAC filters consisting of lossy and lossless integrators have been taken as examples. The strategy of searching begins with generation of the most basic class of graphs-undirected and non-isomorphic. In the next stage undirected arcs are replaced by directed ones, generating from each undirected graph a family of directed ones. And finally the directed graphs changed into signal graphs regarding properties of transfer function. These structures potentially realizing the given transfer function can be implemented as OTA circuits. The introduced strategy partially enables avoiding of the combinatorial explosion problem. The rules controlling search and constraints have been written in the logic programming language-Prolog