31.3 A 950ns 0.5-to-5.5V 5G NR RF PA Supply Modulator with Floating Capacitor Control for Symbol Power Tracking

With the increasing demand for 5G new radio (NR) in which the output power of the RF power amplifier (RF PA) changes rapidly, the fast dynamic voltage scaling (DVS) is required in the supply modulator that provides voltage to the RF PA. In 3GPP requirements, the user equipment (UE) should complete the transmitter (Tx) power change within a transition time defined as $20 \mu \text{s}$ in LTE and $10 \mu \text{s}$ in 5G NR. However, the slower the transition time of the supply modulator, the larger the difference between the output voltage of the supply modulator and the required voltage of the RF PA, resulting in a lower power efficiency and higher error vector magnitude (EVM). For example, because the 5G NR 60kHz sub-carrier spacing (SCS) has a cyclic-prefix (CP) of the length $1.2 \mu \text{s}$ between two symbols and a symbol duration of $16.6 \mu \text{s}$, the conventional average power tracking (APT) supply modulator is not suitable for providing the optimal supply voltage at every symbol period due to the slow voltage transition. Therefore, a symbol power tracking (SPT) that completes the voltage transition within the CP length is required.