A general purpose CAD tool, the IE3D electromagnetic simulator is presented in this article. The simulator is based on an integral equation, a method-of-moment formulation for a full-wave solution of three-dimensional (3D) arbitrarily shaped structures in microwave and millimeter-wave integrated circuits (MMIC), high temperature superconductor (HTS) circuits, microstrip antennas, RF printed circuit boards (PCB), and high speed digital circuit packaging. The primary solution of the simulator is the current distribution on a metallic structure in an environment of multilayered substrates on infinitely extended ground plane. The circuit parameters of the structure in either S-parameter form or RLC-SPICE equivalent circuit form is extracted from the solved current distribution. The simulator consists of an MS-Windows-based layout editor, a schematic editor, an electromagnetic simulator, and a post processor. The simulator can perform stand-alone electromagnetic simulation and optimization and mixed electromagnetic and nodal analysis. Simulation results for structures in various high frequency and high speed domains are presented and compared to measured results. (C) 1994 John Wiley & Sons, Inc.