3.5 GHz WiMAX GaN Doherty Power Amplifier with 2nd harmonic tuning

The paper presents the design, realization, and experimental validation of a GaN-based hybrid Doherty power amplifier for WiMAX base-stations at 3.5 GHz. The amplifier exploits, for the first time as far as authors' knowledge goes, a second harmonic tuning scheme designed to further improve the efficiency in the Doherty region. The amplifier is based on a packaged GaN HEMT from Cree Inc., and shows a saturated output power exceeding 43.2 dBm (21.5W), a Doherty high efficiency region in excess of 6 dB output back-off, with a first peak and maximum drain efficiency at saturation of 55% and 61%, respectively. The amplifier, with baseband digital predistortion, is compliant with the standard emission mask in presence of a 9 dB PAPR WiMAX input, and exhibits a weighted efficiency as high as 40%. The performances of the designed amplifier favorably compare with the state of the art for the same application.