The evolution of linearizers for high power amplifiers

Today, linearization is of enormous importance because of society´s need for greater and greater amounts of information, and the economic and practical restrictions on the spectrum available for its transmission. Interest in reducing distortion is not new. It dates back to early years of radio. Information transmission rate is directly related to distortion level. Linearity and amplifier efficiency are also linked, with higher linearity normally yielding lower efficiency. Thus the development of technology to increase an amplifier´s linearity as means to increase its efficiency is an important piece in the development of linearization. This paper traces the evolution of power amplifier linearization from its inception to the linearizers produced today. It reviews the different forms of linearization and then discusses the roots of modern linearization, which originated from applications in digital wireless communications, and from the needs of the space industry. The state of current linearizer development and limitations is also presented.