Asymmetric Doherty Power Amplifier with Input Phase/Power Adjustment and Envelope Tracking

In this paper, the design and implementation of a Doherty power amplifier (DPA) are proposed using gallium nitride high electron mobility transistors (GaN HEMTs). Class-F and Class-C modes are combined to obtain an asymmetric DPA. The precise active load-pull controlling of fundamental and harmonic terminations of the DPA is simulated and analyzed, including the parasitics of the transistors. The measurements of the DPA with the phase difference, input power ratio adjustment, and envelope tracking of the auxiliary PA are discussed in detail in order to achieve a competitive performance. A greater than 63% drain efficiency is obtained within the 10-dB input power dynamic range at 2.1 GHz. The peak of the drain efficiency reaches 73%, with a corresponding output power of 46 dBm.