Graduation date: 2008Contemporary circuit design involves significant computer-based simulation, calling for a balance between circuit model accuracy and simulation run time. Traditionally, circuit modelers concentrated on producing either (1) physically-based models, where each element in the model correlates to a physically meaningful aspect of the device being modeled or (2) mathematically-based "macromodels," designed to be efficient to simulate without ties to the device's physical underpinnings. While each approach has significant value, the strengths of one are often the weaknesses of the other. This work presents CAM, the Circuit Augmentation Method, that integrates some of the best aspects of each approach. Based on the assumption that high-accuracy, multi-port simulation or measurement data for the device under consideration is available, the methodology augments an existing, user-provided equivalent circuit model that is reasonably accurate over some frequency band with discrepancies elsewhere. Macromodels using rational functions are derived via standard least-squares or vector fittings approaches and are logically "added" to the user model creating a result that is potentially both fast to simulate yet still physically meaningful. An important aspect of CAM is its perturbational nature: It is shown that perturbation of the user model's component values (or similar attributes) is necessary for optimal results. CAM is a general-purpose technique that is applicable to the often difficult problems of modeling circuits requiring wideband accuracy or those incorporating highly-distributed structures. This utility is demonstrated over several two-port examples, including a broadband oscilloscope probe tip, a spiral inductor on a lossy silicon substrate, and a highly-distributed and lossy test circuit.