Multilevel LINC System Designs for Power Efficiency Enhancement of Transmitters

To meet the linearity requirements of novel wireless communication standards using varying-envelope modulations, the class A power amplifier (PA) in the traditional transmitters must be highly backed off to work in the linear region where power efficiency drops rapidly. As for the PA linearization technique, linear amplifier with nonlinear components (LINC), achieves linear amplification without power backoff. However, the combiner power efficiency of the LINC system degrades significantly for signals with a high peak-to-average power ratio. In this paper, we propose a multilevel out-phasing (MOP) scheme to achieve high combiner efficiency by reducing the signal dynamics. Furthermore, based on the MOP, we design two architectures: envelope-adjusting MLINC (EA-MLINC) and gain-adjusting MIANC (GA-MLINC). Under the WCDMA system linearity requirements, the simulations show that 3-level EA-MLINC and 3-level GA-MLINC enhance the LINC system power-added efficiency from 16.5% to 33.4% and 23.6%, respectively.