A CMOS Polar Class-G Switched-Capacitor PA With a Single High-Current Supply, for LTE NB-IoT and eMTC

Abstract

Class-G efficiency enhancement of switched-capacitor (SC) power amplifiers (PAs) requires the power management unit (PMU) to have two high-current power supplies. This paper presents a Class-G efficiency enhancement that only requires one single high-current power supply with a lower bandwidth requirement, significantly simplifying the PMU. The system analysis shows that a transmitter with a resolution of 13 bits and a sample rate of $F_{RF}/2$ meets the requirements of the Cat-M1 and Cat-NB1 standard. The presented PA consists of a number of parallel SC cells. Each cell can be configured in two output-power modes, using only a single supply. At 807 MHz, the peak output power is 27.1 dBm, with an efficiency (PAE) of 33.3%. The efficiency at −6 and −12 dBFS is 22.5% and 14.4%, respectively, which is an improvement of $1.3\times $ and $1.7\times $ compared to Class-B. The 13-bit resolution enables a power-control range for Cat-M1 and Cat-NB1 signals of >63 dB. In that range, the error vector magnitude (EVM) is <4.2%.