A Compact Ka-Band Bi-Directional PA-LNA with 17.4-dBm Psat Using Three-Stack Power Amplifier in 28-nm CMOS

This paper presents a compact Ka-band bi-directional power amplifier-low-noise amplifier (PA-LNA) employing a three-stack PA in a 28-nm CMOS process. In the proposed PA-LNA, the three-stack PA is cross-coupled with a common-source LNA to neutralize gate-drain capacitance of the LNA, enhancing stability and gain in LNA mode. Simultaneously, the three-stack PA achieves higher output power and gain in PA mode. Furthermore, transformer-based matching networks enable fully bi-directional operation within a compact die area. In PA mode, the proposed PA-LNA demonstrates 20.4-dB peak gain with 8.1-GHz 3-dB bandwidth, 17.4-dBm saturated output power (Psat) with 17.2-% peak power-added-efficiency (peak PAE), and –31.5-dB error vector magnitude (EVM) with 256-QAM and 800-MBaud symbol rate at 7-dBm average output power. In LNA mode, the proposed PA-LNA demonstrates 17.3-dB peak gain with 8-GHz 3-dB bandwidth, 5.3-dB noise figure (NF), and 0-dBm input third-order intercept point (IIP3). The core area of the PA-LNA is 0.1 mm2.