A 4.8–6.4-GHz GaN MMIC Front-End Module with Enhanced Back-Off Efficiency and Compact Size

A back-off efficient transmit/receive (T/R) front-end module (FEM) architecture is presented in this paper. On one hand, switchless class-G (SLCG) topology is adopted for power amplifier (PA) to improve the back-off efficiency in TX mode. On the other hand, co-design asymmetric T/R switch scheme is applied to reduce the switch loss in TX path. A 4.8–6.4-GHz FEM is implemented in a 0.15-µm GaN-HEMT process for validation, and the chip size is only 1.45 mm × 1.6 mm. The TX mode realizes a saturated power of 37.2–38.9 dBm and a 6-dB back-off drain efficiency (DE) of 40.2%–43.4%. Applying a 160-MHz LTE signal with 8.5-dB PAPR, an average DE of 33.3%–37% at an average power of 28.3–30 dBm is measured, and the ACPR is better than -46 dBc after digital predistortion. The RX mode achieves a noise figure of 1.8–2.2 dB and an IIP3 of 20.8–25 dBm.