Behavioral Modeling of GaN MMIC Varactors for Tunable Matching Networks

This work proposes an automated framework for the characterization and behavioral modeling of varactor devices, targeting the implementation of tunable matching networks in gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) technology. A preliminary study of various varactor implementations is conducted. For each considered layout, a behavioral approach is applied by vector-fitting the impedance response and automatically synthesizing an equivalent-circuit network. As a case study, the resulting model for an island-type varactor is then used in the design of an integrated tunable matching network, which addresses tracking of the supply-dependent optimum point of power-added efficiency (PAE) of an amplifier stage across different power levels.