Broadband High-Efficiency Watt-Level Millimeter-Wave GaN Power Amplifier for Potential Robust and Cost-Effective 5G RF Front-End Design

This paper presents two broadband highly-efficient millimeter-wave (mm-Wave) Gallium Nitride (GaN) power amplifier (PA) designs that use a common source (CS) 1
^st
stage driving a 2-stack 2
^nd
stage. These PAs cover a key portion of the fifth-generation (5G) FR2-band (i.e., 24 – 44 GHz), using an advanced 40-nm GaN high-electron-mobility transistor (HEMT) technology. The 1
^st
PA was fabricated and achieved saturated output power (P
OUT,sat
) of ~ 21 dBm and peak power-added-efficiency (PAE) of ~ 20% with 3-dB bandwidth (BW) from ~ 20 – 35 GHz in measurement, which are in excellent agreement with the post-layout parasitics extracted (PEX) electromagnetic (EM) simulated data. Therefore, a 2
^nd
Watt-level broadband PA is designed and taped out for fabrication, which attains P
OUT,sat
of ~ 30 dBm with a large 75% fractional BW (3-dB BW from 22 – 48.4 GHz), and peak. PAE of ~ 28% from PEX EM simulations. The data suggests the 2-stage PA can reach P
OUT,sat
> 1 W with high-efficiency broadband performance in the 5G FR2 band by stacking two low-voltage GaN devices in the 2
^nd
stage, making the higher-power GaN PAs attractive vs. silicon PAs for potential 5G mm-Wave applications. We have then compared an all-silicon 5G mm-Wave phased array vs. a design using our Watt-level GaN-based front-end module (FEM) with silicon beamformers. Our calculations suggest the GaN-based FEM can significantly reduce the array size and possibly even cost, and with a considerably wider half-power beam-width (HPBW) to alleviate the blocking effects plaguing mm-Wave communications.