Multi-level Out-Phasing Amplification Technology for Enhancing Efficiency and Linearity of Linear Transmitter

Abstract

There have been many efforts to improve efficiency of transmitter while meeting stringent linearity requirement of modern communication system. Among the technology to enhance efficiency of linear transmitter, the out-phasing technology, also called the linear amplification with nonlinear components (LINC), is considered as promising technology. LINC has been studied long time, since it provides excellent linearity with high efficiency by allowing adopt higg efficient switch-mode power amplifiers. In this paper, various state-of-art techniques for multi-level digital LINC transmitters are presented. For their all-digital implementation, flexible digital phase modulators (DPMs) are used to realize two RF phase input signals in LINC systems. An unbalanced phase calibration technique compensates amplitude/phase mismatches between two parallel paths in the LINC system, and an uneven multi-level LINC structure improves the overall power efficiency. The performance of multi-level LINC technology was experimentally verified for WiMAX signals.