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

Abstract

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.

Doherty Amplifier Linearity Test for Fifth Generation Signals

“…) within our research group, was tested in the ADS for the single PA that operates at 3.5 GHz for the FBMC, FOFDM, and UFMC signals with 50 MHz useful signal bandwidth [3], [4] and for the symmetrical two-way DA that operates at 3.5 GHz for the LTE signals with useful signal frequency bandwidth of 20 MHz, as well as for the FBMC signal with 50 MHz bandwidth [5], [6].…”

“…The DEB_LIN technique was experimentally approved on the ADA for the 16QAM signal with 1 MHz useful signal frequency bandwidth and also for the 64QAM signal with 2 MHz useful signal frequency bandwidth [5], [7], [8]. This linearization technique uses adequately processed baseband signals that modulate the carrier second harmonic, and a detailed explanation of the technique operation can be found in the mentioned literature [3]- [8].…”