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

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 $\mu$m 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 ($R_{\mathrm{L}}$ to 2$R_{\mathrm{L}}$) from back off to saturation, and the value of R
L
is normally related with the input impedance of the employed impedance transformer (IT), which leads to the relatively low R
L
thus limiting the back-off efficiency of DPA. By using a novel complex load modulation, the R
L
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.