A method to increase linearity and/or efficiency of power RF amplifier using a predistortion linearizer WithOUt tuning

摘要

The aim of this paper is to present a new method to perform an RF analog linearization, in which the matching problems between linearizer and power amplifier are minimized. Where complex modulation schemes like 64/128 QAM and OFDM are used, the need of high linearity in RF power amplifier is a major concern. Methods of linearization, in which the signal is predistorted before the power amplifier (PA), have been developed; their performance depends on how good the match between the linearizer and the PA is and, generally, a tuning of the linearizer and a stabilization of the gain of the RF path between the linearizer and the PA is needed. It is suggested to use a phase and amplitude linearizer, placed in the intermediate frequency (IF) path, working with a constant signal power. The linearizer is set on a defined level of Intel-modulation distortion, opposite in sign compared to the PA one, less or equal than the desired value at the PA output. In this way, independently to the characteristics of the specific PA, up to 3 dB increase of the power output of the PA can be obtained maintaining the same Intel-modulation distortion, without the need of tuning the linearizer to compensate the spreading in characteristics of the PA. Insensitivity from the gain variations between the linearizer and the PA is obtained too.