Design of Ka-Band Doherty Power Amplifier Using 0.15 μm GaN on SiC Process Based on Novel Complex Load Modulation

Abstract

In this paper, the design method of Ka-band monolithic integrated circuit (MMIC) Doherty power amplifier (DPA) for 5G wireless communication based on a novel complex load modulation is demonstrated by using Cree’s 0.15 μm Gallium Nitride (GaN) on silicon carbide (SiC) process. Previously, the classical load modulation of DPA relies on the real-to-real transformation of carrier PA output impedance (RL to 2RL) from back off to saturation, and the value of RL is normally related with the input impedance of the employed impedance transformer (IT), which leads to the relatively low RL thus limiting the back-off efficiency of DPA. By using a novel complex load modulation, the RL is not limited by the used IT anymore, which results in the carrier PA can operate with higher output impedance. Consequently, higher back-off efficiency can be obtained. To verify the effectiveness of the design method, a GaN on SiC DPA was designed for 5G applications in a simulation environment. Simulated results of the proposed DPA exhibit drain efficiencies of 37.5% at 6 dB back-off point and 45.5% at the saturation from 26 GHz to 29 GHz.