Design of Asymmetrical Doherty GaN HEMT Power Amplifiers for 4G Applications.

In this paper, a 2-stage Doherty power amplifier and a single class B at 3.800 GHz, based on a 10 W GaN-HEMT technology using the bandwidth up to 6 GHz have been designed. The Doherty structure employes a class B bias condition for the main and a class C configuration for the auxiliary devices in the Agilent’s ADS design platform. An uneven Wilkinson power divider is applied to deliver more power to the auxiliary device in order to achieve proper load modulation. The RF performances of the Doherty amplifier have been compared with those of a class B amplifier alone. The simulation results exhibit that the Doherty architecture can be considered as an ideal candidate for maximizing average efficiency while simultaneously maintaining amplifier linearity.