Linearization of broadband doherty amplifier

Abstract

The linearization of broadband two-way Doherty amplifier for application in the frequency range 0.85-1.15GHz is considered in this paper. The carrier and peaking amplifiers in Doherty configuration comprise Freescale's transistor MRF281S LDMOSFET characterized by the maximum output power 4W and the broadband lumped element matching circuits. The linearization of the amplifier is carried out by the second harmonics and fourth-order nonlinear signals that are extracted at the output of the peaking cell, adjusted in amplitude and phase and injected at the input and output of the carrier cell in Doherty amplifier. The effects of linearization are considered for two tones separated in frequency by 10MHz, 20MHz, 40MHz and 80MHz at different input power levels of 0dBm, 5dBm, 10dBm and 15dBm, as well as for WCDMA digitally modulated signal.