Passive Rational Interpolation-Based Reduction via Carathéodory Extension for General Systems

Passive reduction of interconnects requires the system to be described in the so-called passive form, which limits the application of existing approaches. Passive reduction of a dynamic system in general structure form still remains a difficult problem, and existing solutions are expensive. This brief presents a novel rational interpolation-based reduction framework for reducing the dynamic systems described in any internal structure. The new method is based on the Carathéodory extension, which ensures that the interpolating function is passive without any restriction on the circuit structure. As an explicit moment-matching method, it has a similar computational cost as the Krylov-subspace-based reduction methods and is very efficient to reduce the large systems whose input-output behavior can be approximated by a small number of moments.