A New Modeling Technique for Microwave Multicell Transistors Based on EM Simulations
Antonio Raffo, Valeria Vadalà, Hiroshi Yamamoto, Ken Kikuchi, Gianni Bosi, Norihiko Ui, Kazutaka Inoue, G. Vannini
Abstract
Dealing with high-power operation (i.e., >100 W) is extremely critical to power-amplifier designers due to the lack of accurate transistor models of multicell (i.e., powerbar) devices. The reason is twofold: from one side, it is extremely difficult to characterize high-power transistors (e.g., device instability, thermal issues, microwave instrumentation costs, and measurement uncertainty that drastically increases with the investigated power level); and from the other side, the scaling proprieties of the model, moving from the unit-cell device to the multicell one, are inherently poor due to the different passive access structures to the active-device area. In this article, for the first time, an accurate modeling technique oriented to multicell devices is described, which allows one to extract a compact model of a multicell transistor showing similar prediction accuracy of the unit-cell one. Our assumptions have been widely demonstrated in the manuscript by a comprehensive characterization campaign from small- to large-signal operations carried out on both the unit- and multicell devices.