A Wideband and High Efficiency Ka-band GaN Doherty Power Amplifier for 5G Communications

Abstract

This paper presents a wideband and high efficiency Ka-band gallium nitride (GaN) doherty power amplifier (DPA) fabricated by 0.15μm GaN-HEMT on SiC technology. The Tee-line network impedance inverter which is formed utilizing output capacitance of transistors was designed to increase operation bandwidth. Moreover, it was possible to realize the impedance inverter at millimeterwave band by using Metal-Insulator-Metal capacitor on via-holes (MIM -on-Via) structure which can decrease parasitic inductances. As a result, the fabricated 2-stage DPA has achieved a measured saturation output power of 36.1-36.5dBm, a 6dB back-off PAE of 25-27%, and a peak PAE of 26.7-31.8% in the frequency band of 26-30GHz. This fractional band is 14.6%. To the best of authors' knowledge, this performance is the widest bandwidth with high efficiency in Ka-band GaN DPA. Additionally, the measured ACPR is -31.1dBc and EVM is 3.2% at the average output power of 28dBm under 45MHz 64QAM modulated signal.