A 22W 65% Efficiency GaN Doherty Power Amplifier at 3.5 GHz for WiMAX Applications

The design, implementation and characterization of a Doherty Power Amplifier (DPA) for 3.5 GHz WiMAX applications are discussed. The DPA has been implemented using a commercial GaN HEMT from Cree inc., following a class AB and C scheme for the main and peak module, respectively. The measured maximum power of the DPA is 22W with a first peak efficiency of 57%, and maximum drain efficiency of 65% at the DPA saturation. Efficiency over the so-called Doherty region (where both the main and the peak amplifiers operate) does not drop below 55% from saturation to 6 dB input back-off. The gain at the onset of the Doherty region is 8 dB, with around 1 dB roll-off.