Analysis of Back-Gate Bias Control on EVM Measurements of a Dual-Band Power Amplifier in 22 nm FD-SOI for 5G 28 and 39 GHz Applications

Abstract

This paper presents a dual-band power amplifier (PA) covering the 5G n257 to n260 frequency 2 bands (24.25 to 29.5 GHz and 37 to 43.5 GHz), fabricated in the 22 nm fully-depleted silicon-on-insulator (FD-SOI) CMOS technology. Its design is based on a distributed balun at the output that efficiently performs a wideband load impedance transformation. The back-gate terminal of each transistor is connected to different pads for detailed back-gate bias variation analysis. Under 5G new radio (NR) modulated signal measurements, we show how the average output power and efficiency can be optimized by varying the back-gate bias, which optimal value depends on (i) the signal bandwidth, (ii) the carrier frequency and (iii) the target error-vector-magnitude (EVM) value. To the best of the authors’ knowledge, the impact of back-gate bias control on the system-level EVM figure of merit is shown for the first time in this work. Overall, with 7.5 dBm and 7.3% mean output power and efficiency, respectively, at 27 GHz, 6 dBm and 5% at 40 GHz, for a 800 MHz bandwidth 5G NR signal, the presented PA shows outstanding performance among wideband/multiband FD-SOI-based PAs covering the 28 and 39 GHz bands, featuring comparable performance to best-in-class narrowband PA designs in FD-SOI technology.