15.2 A 90ns/V Fast-Transition Symbol-Power-Tracking Buck Converter for 5G mm-Wave Phased-Array Transceiver

Abstract

The 5G-New-Radio (NR) standard in millimeter wave (mm-wave) bands requires a low-cost antenna module consisting of a phased-array transceiver with beamforming [1], an antenna array, and a power management IC (PMIC). Since a typical on-chip mm-wave CMOS power-amplifier (PA) arrays have poor power efficiency due to the lossy substrate and the low maximum available-gain frequency of CMOS processes, they cause serious thermal issues due to the high power density and reduce battery life in a mobile handset. Recently, supply-modulation (SM) techniques, such as an envelope tracking (ET) and an average-power tracking (APT) instead of a direct battery-connected supply, have been introduced to enhance PA efficiency [2]. However, these techniques have few challenges, such as limited ET tracking bandwidth and APT transition time, to support new requirements of the 5G NR standard. In order to manage the power effectively of a phased-array module, a special SM technique named symbol-power tracking (SPT) is proposed for the power management in this work. The SPT controls the supply voltage of mm-wave PA arrays every few micro-second (symbol to symbol), which is much faster than that of APT, which adjusts the output voltage every one millisecond (sub-frame to sub-frame).