Extended subspace identification of improper linear systems

Abstract

The modeling of linear transfer functions is often required prior to the simulation of electronic systems. An example is the modeling of on-chip inductors starting from 2-port measurements. The modeling is often done using state-space models that can only represent proper systems. This leads to modeling problems in the case of improper systems such as in the case of 2-port modeling of the admittance matrix of an on-chip inductor. This paper first describes an extended state-space model to represent improper systems. Afterwards, the paper introduces an extension to classical frequency-domain subspace identification methods. The usefulness of both the extended state-space model and the extended subspace modeling technique are illustrated by comparing them with commercially available solutions. This includes a comparison on measurements of an on-chip inductor and on simulations of a coplanar waveguide.