Linearization of GaN power amplifier using feedforward and predistortion techniques

This paper investigates the feasibility of linearizing GaN power amplifier using the diode-based predistortion and the feed-forward techniques. For the diode-based predistortion technique, a new strategy is presented for selecting the breakpoints on a typical linearizer characteristic. Using this strategy, a new diode-based curve-fitting predistortion linearizer for GaN power amplifier is developed. The proposed linearizer is tested using the two-tone test. The experimental results show that a 3 dB improvement in the overall gain of the linearized amplifier is achieved. Moreover, for output power levels up to 36 dBm, the linearized power amplifier provides better rejection of the third-order intermodulation. Because of the hard nonlinearity of the GaN power amplifier at the high end, this improvement in intermodulation rejection vanishes for output power levels around 41 dBm. For the feedforward technique the simulation results show that the 1 dB compression point has been increased from the original 40 dBm for unlinearized amplifier to 43.74 dBm for the linearized one.