Linearization of a 3.7 GHz multi-carrier GaN HEMT Doherty power amplifier using digital predistortion method

Abstract

In this article, a 3.7 GHz band Doherty amplifier based on GaN HEMTs, which is linearized using a digital predistortion method, is implemented for 4th generation wireless communication systems. The forward and reverse models of the Doherty amplifier for the predistortion consist of simple polynomials whose coefficients are extracted using a conventional least mean square error algorithm. Using a two carrier signal based on IEEE802.16e, whose PAR is 9.44 dB, an ACLR improvement of 10.74 dB is achieved to give an ACLR level of 41.74 dBc at an offset of 4.79 MHz. The overall efficiency of the Doherty power amplifier is 13.74%, which represents a 2.44% improvement compared with that of a balanced class-AB power amplifier at an average output power of 36 dBm. © 2010 Wiley Periodicals, Inc.