Evaluation of GaN technology in Doherty power amplifier architectures

The aim of the present paper is to highlight the possible benefits coming from the use of the GaN high electron-mobility transistor (HEMT) technology in the Doherty power amplifier (DPA) architecture. In particular, the attention is focused on the capabilities and the relevant drawbacks of a GaN HEMT technology when designing DPAs. A deep discussion of the DPA's design guidelines is also presented through the realization of three prototypes implementing different design solutions and working at 2.14GHz. The first example is a tuned load DPA (TL-DPA), which show an average drain efficiency of 40.7% with 3 W of saturated output power in the obtained 6dB of output back-off. The second DPA was designed implementing a class F harmonic termination for the main device, which allows an improvement of roughly 15% in output power and efficiency behavior with respect to the TL-DPA. The last DPA was realized implementing a single output matching network for both main and auxiliary devices, which allows a relevant reduction in the size of the resulting DPA, without downgrading the overall performances.