Techniques to Improve Power Amplifier Energy Efficiency for 5G

Improved spectral and energy efficiency are two key requirements for the fifth generation (5G) wireless communication systems. The inefficiency and non-linearity of traditional power amplifiers (PA) pose significant challenges to meet these requirements, especially for multicarrier modulation signals (MCM) with high peak to average power ratio (PAPR). In this paper, we study methods to improve the energy efficiency of PAs and compensate for the distortion of PA non-linearity. A low complexity envelope tracking (ET) method where the supply voltage of the PA consists of two or more discrete levels is presented. To reduce the distortion due to PA nonlinearity, a power amplifier model with power supply variation is introduced and a digital predistortion technique based on a Volterra series is used. Finally, an integrated architecture combining crest factor reduction (CFR), DPD, and ET is presented. Simulations and measurements from a hardware platform demonstrate the energy efficiency gains attained by the proposed techniques.