VNA-Based Testbed for Accurate Linearizability Testing of Power Amplifiers Under Modulated Signals

Abstract

This paper presents a vector network analyzer(VNA) based testbed for accurate power amplifier (PA) linearizability testing under wideband modulated signals. The proposed testbed utilizes two of the VNA’s receivers to simultaneously capture the calibrated input and output signals of the PA. The testbed corrects the linear and nonlinear distortions exhibited by the underlying components (e.g., arbitrary waveform generator, up-converter, driver amplifiers, and couplers) so that the linearizability testing is solely indicative of the performance of the PA under test. Experiments conducted using two PA demonstrators confirmed the capacity of the proposed testbed to support digital predistortion based linearization testing under 5G NR OFDM test signals with modulation bandwidths (e.g., 200 MHz) that significantly exceed the VNA receivers bandwidth. More importantly, the pre-correction of the linear and nonlinear distortions yielded an improvement of the adjacent channel power ratios at the output of the PAs by up to 7 dB compared to the uncorrected case.