Asymmetrical Continuous Mode Doherty Power Amplifier Using Complex Combining Load Impedance

This work presents a broadband asymmetrical continuous-mode class J Doherty power amplifier (PA) using complex combining load. The DPA functions as a class J PA when operating in the low power region. The proposed Doherty PA (DPA) achieves continuous mode class J characteristics by varying the reactive part of the complex load. This variable complex combing load has been realized by a novel post-matching network (PMN). A detailed theoretical analysis is presented that shows the impedance transformation procedure from the asymmetrical DPA impedance trajectory to a class J. To validate the proposed technique, a prototype PA has been designed with Cree GaN devices for 9 dB output power back-off (OBO) operating from 1.8 GHz to 2.6 GHz. In the aforementioned frequency band, the PA achieves 61%–76% efficiency at saturation and 43%–60% efficiency at OBO. The PA maintains 10 dB gain and an average of 43 dBm power over the entire frequency range.