During a post-doc at inria in collaboration with the FACTAS team, I developed a stability analysis tool called PISA. The code is now available at adamcooman.gitlab.io/pisa-stability-analysis It is licensed under the AGPL.

Below you can find the papers related to this stability analysis.

Stability analysis using projection

We developed a stability analysis based on projection instead of approximation. This stability analysis is perfectly suited to handle circuits with distributed elements, like transmission lines, because it does not require a rational approximation.

Estimating unstable poles in microwave circuits

A refinement of the stability analysis above. We improve the filter used in the analysis and use Kung’s method after projection to obtain a very accurate estimate of the location of the unstable pole, even when the circuit contains distributed elements.

Circuit transfer functions

One of the foundations of the projection-based stability analysis is that a circuit can only have a finite amount of unstable poles. The proof for this statement is detailed in this paper.