Rethinking Microwave Power-Bar Characterization

In this paper, we propose a new measurement setup for the characterization of microwave power bars up to 150 W. By operating at low-frequency (i.e., a few megahertz), it overcomes the limitations of microwave systems and enables the characterization of the power-bar resistive behavior under conditions consistent with high-frequency operation. Such a kind of characterization provides data that can be directly used to enhance nonlinear model accuracy by overcoming the limitations of state-of-the-art power-bar models obtained by simply scaling the behavior of the unit-cell device. In fact, thermal and trapoccupation states, as well as distributed (passive) access structures to the device active area, do not scale with the periphery in powerbar devices. The setup has been fully validated by characterizing a 130-W GaN power bar under class-E operation. Measurement results have then been used for the design of a VHF power amplifier.