Broadband Doherty power amplifier with improved band‐pass auxiliary network

Abstract

In this article, a Doherty power amplifier (DPA) with improved band-pass auxiliary impedance inverter is proposed for broadband operation. As a wideband DPA solution, the output matching networks of main and auxiliary devices are designed to achieve proper impedance matching at back-off and peak power by employing a two-point matching technique without the λ/4 impedance transformer. It is found that the modified band-pass network has broader bandwidth feature and is compact in form from the comparison with some different topologies of matching networks. So, it is more suitable to be the auxiliary transformer to achieve the broadband configuration of DPA. For validation purpose, a Doherty power amplifier based on two commercially available gallium nitride HEMT (Cree CGH 40010F) devices was designed, fabricated, and measured. Under the drive of continuous wave (CW) signal, the measurement results show that the DPA has a 6-dB back-off efficiency of 35% to 48% and a saturated efficiency of 44% to 64% within the frequency band from 1.50 GHz to 2.35 GHz, which is about 44% fractional bandwidth.