Passivity-preserving model order reduction of linear time-varying macromodels

We study model order reduction (MOR) of continuous-time linear time-varying (LTV) systems. Examples include circuit or interconnect models found in VLSI marco-modeling. Specifically, a time-varying version of positive-real balanced truncation (PRBT), called LTV PRBT, is proposed, which preserves the passivity of LTV systems for stable global simulation. Implementation details are discussed together with a brief outline of a discrete-time counterpart of LTVPRBT. Dynamically changing state dimension is allowed for accurate modeling at the lowest possible order. Numerical examples then verify the effectiveness of the proposed approach over existing LTV MOR methods.