A Wideband Sub-6-GHz Transceiver Front End for 5G Base Stations in 22-nm FD-SOI CMOS

A fully integrated, non-frequency-translating, low-impedance transceiver (TRX) front end for cellular base stations (BSs) covering 1.25–5.5 GHz is presented. The transmitter (TX) features two variable gain feedback pre-power amplifier (PPA) stages, a power amplifier (PA), and an RF notch filter based on frequency translation for suppressing spurious signals. The receiver (RX) features a low noise amplifier (LNA), a variable gain amplifier (VGA), and an equalizer supporting three concurrent frequency bands with orthogonal frequency and gain tuning. The PA and LNA use a 12.5- $\Omega $ differential impedance, primarily to boost PA output power and bandwidth (BW). Special emphasis is put on the thermal analysis of the PA and the techniques to improve the cooling. When operating with full PA supply (7.4 V), including antenna-switch and package losses, the TX reaches a record saturated output power ( $P_{\mathrm {sat}}$ ) of 38.1 dBm at 3.4 GHz, and for a 100-MHz 16-QAM orthogonal frequency-division multiplexing (OFDM) signal at 2.7 GHz, the TX delivers an output power of 32.6 dBm with an error vector magnitude (EVM) of -17.6 dB, with a complete TX efficiency of 13.5%. With a reduced PA supply of 3.8 V, an ${8} {\times } {100}$ MHz 256-QAM OFDM signal with 21.6 dBm was measured with EVM ${\lt } {-}31.1$ dB. The TX filter achieves about 40-dB notch depth at 1–6-GHz notch frequencies, and the 20- and 30-dB rejection BW can be controlled from 1 to 10 MHz and from 0.4 to 4 MHz, respectively. The front end has an RX noise figure (NF) of 1.3–2 dB, while the third-order intercept point (IIP3) is above -12.4 dBm, at maximum gain (29 dB) over the frequency range of 1.55–4.8 GHz. The passive equalizer improves the RX interference handling and is analyzed using closed-form expressions. The active part of the die, manufactured in 22-nm fully depleted silicon on insulator (FD-SOI) CMOS technology, occupies 6.6 mm2.