A Compact 24–30-GHz GaN Front-End Module With Coupled-Resonator-Based Transmit/Receive Switch for 5G Millimeter-Wave Applications

This article presents a wideband front-end module (FEM) topology with integrated transmit/receive (T/R) switch utilizing a matching network (MN) reuse technique. The output MN (OMN) of the power amplifier (PA) and the input MN (IMN) of the low noise amplifier (LNA) are reused in the switch network co-design, enabling T/R switching and impedance transformation simultaneously. In TX mode, a switchless MN incorporating RX reactance is employed to improve the output power and efficiency. In RX mode, the OMN of the PA serves as an extra resonant tank and can be absorbed into the RX MN to enhance RX bandwidth and noise performance. To validate the proposed FEM topology, we implemented a 24–30-GHz FEM for 5G millimeter-wave (mmWave) applications using a commercial 0.15- $\mu $ m gallium nitride (GaN) high-electron-mobility transistor (HEMT) process. The TX branch achieves a small-signal gain greater than 17 dB, a 14.5%–17% saturated power-added efficiency (PAE), and 27.4–29.5-dBm saturated output power. The average output power, measured at an error vector magnitude (EVM) of less than −25 dB, is 21.9 dBm with an average PAE of 4%. The RX branch demonstrates a small-signal gain of 18.5 dB, a noise figure (NF) of less than 4.4 dB, and an OP $_{\text {1, dB}}$ of 12 dBm. In addition, the chip area is only $2.1\times 2.6$ mm.