부산대학교 도서관

This article presents a modified transmit/receive (T/R) front-end module (FEM) architecture with improved transmitter (TX) efficiency. Single-pole double-throw (SPDT) switch is commonly adopted in conventional FEM for T/R isolation, but its insertion loss (IL) deteriorates TX efficiency greatly. To alleviate this problem, a post-matching (PM) architecture is proposed to eliminate the switch in the TX branch. Specifically, a PM network (PMN) is employed to transform 50- $\Omega $ impedance at the antenna port into the intrinsic optimal load impedance of the power amplifier (PA), while the output capacitance of the PA is absorbed into a $\lambda $ /4-transmission-line (TL)-based single-pole single-throw (SPST) switch in the receiver (RX) branch. The drain voltage of the PA can also be supplied via the SPST, avoiding the use of an additional choke inductor. The theoretical performance of the T/R switch, including bandwidth, IL, and isolation, is analyzed in depth. A 4.9–7.1-GHz FEM for Wi-Fi 7 application is implemented in a commercial 0.15- $\mu \text{m}$ gallium nitride (GaN)-high-electron-mobility transistor (HEMT) process to validate the proposed architecture, and the chip size is only 2 $\times $ 1.6 mm. The TX mode realizes a saturated power of 37.1–38.6 dBm and a saturated power-added efficiency (PAE) of 45%–52.4%. With MCS9 EHT160 signals, an average PAE of 18.5%–23.3% at an average power of 28–29.9 dBm is measured, while the error vector magnitude (EVM) specification of – 32 dB is met. When digital predistortion (DPD) is applied, MCS13 EHT320 signals are also supported. The RX mode achieves a gain of 9.1–12.1 dB, a noise figure (NF) of 1.6–1.9 dB, and an input-referred third-order intercept point (IIP3) of 20.2–25.4 dBm.