A 600W broadband doherty power amplifier with improved linearity for wireless communication system

An asymmetric Doherty architecture based on three identical transistors is proposed in this paper. This proposed three-way topology reduces the difficulty in designing matching networks brought by the low optimal impedance of high power transistors. And the inverted Doherty topology as well as carefully chosen value of load impedance makes it possible to extend the bandwidth of high power amplifiers. Besides, bias networks of this proposed three-way architecture are also carefully considered to improve the linearity. The proposed high power three-way Doherty power amplifier (3W-DPA) is designed and fabricated based on theoretic analysis. Its maximum output power is about 600Watts and the drain efficiency is above 35.5% at 9dB back off output power level from 1.9GHz to 2.2 GHz and the saturated drain efficiency is above 47% across the whole frequency band. The measured concurrent two-tone results suggest that the linearity of DPA is improved by at least 5dB.