15.1 An 88%-Efficiency Supply Modulator Achieving 1.08μs/V Fast Transition and 100MHz Envelope-Tracking Bandwidth for 5G New Radio RF Power Amplifier

• Published in: 2019 IEEE International Solid- State Circuits Conference - (ISSCC) pp. 238 - 240
• Main Authors: Paek, Ji-Seon, Kim, Dongsu, Bang, Jun-Suk, Baek, Jongbeom, Choi, Jeonghyun, Nomiyama, Takahiro, Han, Jaeyeol, Choo, Younghwan, Youn, Yongsik, Park, Euiyoung, Lee, Sungjun, Kim, Ik-Hwan, Lee, Jongwoo, Cho, Thomas Byunghak, Kang, Inyup
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.02.2019
• Subjects: 5G mobile communication; Bandwidth; Capacitors; Field-flow fractionation; Modulation; Power generation; Voltage control
• ISSN: 2376-8606
• DOI: 10.1109/ISSCC.2019.8662460

In the recent 3GPP standard, 5G New Radio (NR) in the sub-6GHz frequency band supports up to 100MHz bandwidth (BW) for uplink channel and requires fast on/off transition below 10 \mu \mathrm {s} to support short transition-time interval (TTI). Thus, it forces the supply modulator (SM) to track the NR-100MHz envelope signal for power saving of an RF power amplifier (RF-PA) and requires a fast dynamic voltage-scaling (DVS) transition. For the 3G/LTE uplink, the SM has to satisfy low receiver-band noise (RxBN) for LTE-FDD bands [1] and a boosted output for Power Class 2 high-power user equipment (HPUE) in TD-LTE [2], [3]. In order to support the 100MHz envelope tracking (ET) BW, the SM must have a 3dB bandwidth of at least 125MHz while keeping sufficient phase margin in the presence of few-hundred-pF load capacitance. Furthermore, a typical linear-assisted SM topology has maximum efficiency limitation due to the AB bias current, sinking- and sourcing-current of the linear amplifier. In this work, a voltage-buffer-compensated (VBC) Class-AB linear amplifier (LA) and a feed-forward fast-switching (FFFS) buck converter are proposed to achieve the 100MHz ET BW and high system-power efficiency.