Wideband envelope tracking power amplifiers for wireless communications

Envelope tracking (ET) RF power amplifiers are emerging from decades of research as practical approaches for highly efficient, highly linear, broadband power amplification. Many aspects of ET power amplifiers are ideally suited for modern wireless communications - they work well across a wide frequency range, they are amenable to high levels of integration at the mobile terminal level, and they will continue to improve as Moore's Law scaling of digital circuits allows for increasingly sophisticated algorithms to improve linearity and efficiency. At the same time, some genuine challenges for ET power amplifiers remain, particularly in the areas of efficiency, modulation bandwidth, and receive band noise. This paper will summarize the varying challenges of applying this exciting new technique to emerging wireless standards.