Design of Broadband Doherty Power Amplifier with Extended Efficiency Range Employing Asymmetric Structure

In this paper, the method of designing broadband Doherty power amplifier (DPA) with extended efficiency range is proposed. The carrier power amplifier operates in a continuous class-F mode to extend the bandwidth. Meanwhile, the peaking power amplifier operates in class-C mode. Additionally, the asymmetric structure is employed to extend efficiency range. A broadband DPA working across 1.8 to 2.6 GHz (bandwidth of 800 MHz) is designed and fabricated for validation. The fabricated power amplifier delivers 49.6-63.4% drain efficiency at 9-dB output back-off power levels and 51.4-67.8 % at peaking power levels with the peaking output power of 44.8-45.2 dBm. A 20 MHz LTE modulated signal with 7.6 peak-to-average power ratio is used to measure the linearity of the fabricated DPA. Results show the adjacent channel power ratios are -25 and -45 dBc respectively before and after digital predistortion.