Time-Domain Characterization and Linearization of a Dual-Input Power Amplifier Using a Vector Network Analyzer as the Receiver
Thaimí Niubó-Alemán, Chenyu Liang, Yunsik Hahn, J. A. Reynoso‐Hernández, Jean-Pierre Teyssier, Patrick Roblin
Abstract
A newly calibrated testbed based on a commercial vector network analyzer (VNA) is proposed for the fast in-band vector signal characterization and linearization of nonlinear multiport devices. The testbed can acquire both CW and wideband modulated periodic signals without breaking contact with the DUT, in up to five channels. The time-domain measurements are made possible by calibrating all the receivers in the frequency domain. This calibration provides a phase and amplitude correction for the modulation tones of all the incident and reflected waves in the acquisition bandwidth. The measurement bandwidth is determined at calibration by the bandwidth of the periodic OFDM signals used as a phase standard. It is independent of the VNA receivers' bandwidth. A 500-MHz 100 000-tones 64-QAM OFDM constellation is recovered with 0.48% error vector magnitude (EVM). As an application, a dual-input hybrid Doherty-outphasing power amplifier (HD-OPA) is characterized at 2.08 GHz. A CW signal is used to determine the outphasing angle and input power levels, which provides the best drain and power-added efficiencies for each output power. The dynamic response of the dual-input HD-OPA is acquired on five channels by using the same testbed. Various periodic OFDM signals, with 24 000 tones, are measured before and after predistortion linearization in a fraction of a second.