A GaN-Based MMIC Doherty Power Amplifier with Class F Peaking Branch

This paper presents a novel design approach to enhance the performance of the Peaking branch of a Doherty Power Amplifier (DPA), by properly manipulating its input harmonics through a suitable nonlinear driver stage. In particular, aiming to implement a Class F harmonic termination for the final stage, a third harmonic voltage component is injected at its input with a driver, so that the phase of the third harmonic current at the output of the final stage is reversed with respect to its normal evolution, allowing a Class F design strategy for a class C biased device. The design strategy is described together with the design and experimental characterization of a prototype for X-Band application. The DPA is realized on the 120 nm gate-length GaN-on-SiC technology available at WIN Semiconductors. The MMIC provides more than 36 dBm and 40% of output power and efficiency, respectively, at 10 GHz.