Abstract: An automated technique for the design of microwave and similar circuits using a knowledge based computer system containing a library of fixed-topology circuits and an associated store of knowledge concerning the performance and limitations of these circuits over a variety of operating conditions. The method of the invention permits a relatively unskilled user to specify a circuit by performance parameters only, and to obtain as an end product a coded output that will drive a conventional mask fabrication system used to produce the circuit. Important features of the invention include its use of a unified data structure in which both physical and electrical characteristics of every circuit element are stored together in the rationally consistent manner to facilitate circuit layout, and its use of a circuit compaction procedure that makes use of the unified data structure and minimizes the circuit area without adversely affecting electrical circuit performance.