A High Efficiency Multi-Mode Outphasing RF Power Amplifier With 31.6 dBm Peak Output Power in 45nm CMOS

Abstract

A high efficiency multi-mode class-E outphasing RF power amplifier (PA) with a passive combining circuit is presented. The multi-mode PA combines multiple class-E amplifier branches and can work in different configurations. The PA improves efficiency at lower power levels by switching ‘on’ and ‘off’ individual branches in a static or dynamic manner and using Efficiency Enhancement Circuit (EEC). The proposed power amplifier is designed in 45nm CMOS technology. The PA delivers 31.6 dBm peak output power at 2.4 GHz with 49.2% drain efficiency in high power single level mode. With 64-QAM long-term evolution (LTE) signal with 10 MHz and 20 MHz bandwidth, −57 dBc and −53 dBc adjacent channel power ratio (ACPR) are obtained in single level outphasing (SLO) mode after digital pre-distortion (DPD). 25% and 33% average drain efficiency are achieved with LTE signal with 6 dB peak-to-average power ratio (PAPR) in single level outphasing and asymmetric multilevel outphasing (AMO) mode, respectively. The PA satisfies the spectral mask requirement of 802.11g WLAN signal with high margin. Error vector magnitude (EVM) of 1.1% (−39.36 dB) is obtained from the PA in single level outphasing high power mode after DPD with 64-QAM LTE signal with 10 MHz bandwidth.