Design of a 37-40GHz bidirectional amplifier for 5G FR2 radio beamforming systems in 22nm CMOS FD-SOI

This paper presents the operation of a bidirectional amplifier (PA-LNA) for digital beamforming (DBF) radio systems within the 5G FR2-1 n260 frequency band ranging from 37GHz to 40GHz, using the GlobalFoundries 22nm CMOS FD-SOI technology. This amplifier is intended to be integrated into a complete bidirectional transceiver. The PA-LNA consists of a transformer-based differential architecture and interconnected differential pairs using NMOS and PMOS transistors both enabled using tale transistors. This solution eliminates the need for lossy TRX SPDT (Single Pole Double Throw) switches, conventionally used to address alternatively the PA or the LNA in order to operate in time division duplexing (TDD). In this design, matching networks are reused leading to a strong required area reduction, close to a factor of two, compared with conventional architectures. The proposed PA-LNA achieves a small signal gain of 14.4dB in PA mode and 23.8dB in LNA mode. In PA mode, it achieves a saturated output power (Psat) of 7.5dBm and a 7.1dBm OCP1 consuming a static DC power of 11.6mW with a 27.4% power added efficiency (PAE) at OCP1, while the LNA mode achieves a noise figure (NF) of 4.6dB consuming a DC power of 21mW. The core area of the amplifier is only 0.11mm$^{2}$.