Design of Dual-band Asymmetric Doherty Power Amplifier Based on Combined Output Network

To enlarge the back-off power range of the Doherty power amplifier (DPA) in dual-band mode and improve its efficiency, a dual-band asymmetric DPA using a combined output network is proposed. After employing a dual-peaking amplifier structure, the peaking impedance transforming network is designed by the two-point matching design method, which improves the bandwidth of the dual-band DPA. A specially designed transmission line with dual-band characteristics using phase periodicity principle is introduced to convert the short circuit at the output of the combined peaking amplifier matching network to the output impedance required by the carrier amplifier at the back-off state. A 2.35-2.75 GHz and 3.2-3.6 GHz dual-band DPA was fabricated and measured. The measurement results show that the designed DPA achieves efficiencies of 55%-66.5% and 46%-67.5% at saturation, and the efficiencies at the 9 dB power back-off point reach 41.5%-53.3% and 40.5%-52.8%, respectively.