Experimental Verification of the Impact of the 2nd Order Injected Signals on Doherty Amplifiers Nonlinear Distortion

In this paper, an asymmetrical Doherty amplifier fabricated in microstrip technology is tested in the experiments to verify the impact of the 2^nd order signal for the linearization prepared in baseband. The measurement set-up consists of three USRPs programmed by LabVIEW to generate the useful 64QAM signal and the signals for linearization that are set in amplitude and phase and modulate the 2^nd harmonic of fundamental carrier. The USRPs instruments should be synchronized for performing measurements for two scenarios: the signals for linearization are injected at input of the transistor within the main Doherty amplifier or are injected at its output.