On generating compact, passive models of frequency-described systems

Increasing system integration and tighter design constraints and specifications make it necessary to account for the non-ideal behavior of all the elements in a system. For high-speed digital, and microwave systems, it is increasingly important to model previously neglected frequency domain effects. In this context, the problem of creating time domain models from tabulated frequency data, representing a device´s input-output relationship is of paramount importance. Such models must possess acceptable accuracy and also be very compact as they may be extensively used in later simulations. An important class of devices that are often described by, tabulated frequency domain data is that of passive devices. In this paper we discuss several two-step algorithms based on a combination of rational interpolation with standard model order reduction procedures that is aimed at generating accurate multiport models from tabulated S-parameter data. We show that important system properties such as passivity can be maintained while generating compact models that are amenable to direct inclusion in standard time-domain simulators.