An Open-Source EM Simulation Flow Based on a High-Level Python API

We present a high-level Python API that enables a fully open-source electromagnetic (EM) and EM-circuit co-simulation flow. The API integrates OpenEMS for 3D full-wave EM simulation, automating critical tasks such as GDSII import, port definitions, meshing, and sequential multi-port excitation to generate the S-parameter matrix. Another key contribution of this work is integration of Xyce for circuit-level characterization, and the implementation of vector fitting techniques to convert multi-port S-parameters into SPICE sub-circuit models, overcoming the limitation of all open-source circuit simulators that only support two-port S-parameter files. This approach enables integration of multi-port RF components into large-signal and small-signal simulations, mirroring the capabilities of commercial design tools. The proposed API is fully modular, supporting multiple open-source PDKs, arbitrary passive networks, and various circuit configurations.