Design strategy of a 2.8-3.6 GHz 20W GaN Doherty power amplifier

This paper presents the design of a 20W GaN Doherty Power Amplifier working in the range 2.8 GHz-3.6 GHz. The design strategy adopted for the design of the Doherty output combiner is discussed, which consists in embedding the device parasitics into the latter, implemented as a multi-stage quarterwavelength transformer, in order to achieve wideband behaviour. The saturated output power ranges from 42dBm to 44 dBm, with a corresponding drain efficiency in excess of 47%. The efficiency at 6 dB of output back-off is higher than 42% over the whole frequency band, and the small-signal gain is higher than 10 dB. Due to the discrepancies of the measured scattering parameters compared to the simulated ones, which could not be corrected with post-tuning, a redesign of the prototype is ongoing.