A 29.5 dBm Class-E Outphasing RF Power Amplifier With Efficiency and Output Power Enhancement Circuits in 45nm CMOS

Abstract

A CMOS class-E outphasing RF power amplifier is presented with a new passive combining circuit that provides high efficiency and high output power. An efficiency enhancement circuit and a power enhancement circuit are proposed as part of the combiner that improve efficiency at power back-off and increase output power without violating reliability limits, respectively. The proposed power amplifier is designed in a 45nm CMOS technology. The power amplifier (PA) delivers 29.5 dBm peak output power at 2.4 GHz with 46.76% drain efficiency at peak output power, 32.96% drain efficiency at 3 dB power back-off, and 21.16% drain efficiency at 6 dB power back-off. The proposed power amplifier shows excellent linearity with digital pre-distortion. Better than -50 dBc adjacent channel power ratio (ACPR) is obtained with 64-QAM long-term evolution (LTE) signal with 10 MHz and 20 MHz bandwidth. For two-carrier 20 MHz LTE signal, -44 dBc ACPR is achieved. 21% average drain efficiency is obtained with LTE signal with a 6 dB peak-to-average power ratio. The PA is also tested with 802.11g WLAN signal and it satisfies the spectral mask requirement with high margin. 1.4% (-37.1 dB) error vector magnitude (EVM) is obtained with LTE signal (64-QAM) with a 10 MHz bandwidth.