24.8 A W-Band Power Amplifier with Distributed Common-Source GaN HEMT and 4-Way Wilkinson-Lange Combiner Achieving 6W Output Power and 18% PAE at 95GHz

W-band power amplifiers (PAs) play an important role in Gb/s-data-rate wireless communication, imaging, and radar applications. Traditionally, multiple transistors are connected in parallel to maximize the output power. Though the active area, including gate width and number of fingers, can be scaled up to generate large transistors, the metallic inter-connection is not suitable for scaling due to random shape and magnetic coupling. Thus, an accurate device model should be investigated by separating the scalable and the non-scalable parts. In additional, the maximum output power of the PA is known to be limited by intrinsic characteristics of power transistor, such as maximum current density, breakdown voltage, and parasitic element. Compared to silicon-based technology, GaN PAs are able to operate at higher voltages and frequencies, thereby reducing loss and improving power density (W/mm ² ) [1].