VNA-Based Large-Signal Drain-Modulated Power Amplifier Measurement Setup With Digital Pre-Distortion

In this work a Vector Network Analyzer (VNA)-based large-signal drain-modulated measurement setup with simultaneous input and output signal extraction and Digitial Pre-Distortion (DPD) for Power Amplifier (PA) characterization is discussed. The proposed architecture is capable of handling coherent wideband modulated signaling with a calibrated reference plane down to the tip of the wafer probes, making it resilient to component changes outside the VNA directional couplers like signal generators and pre-amplifiers. Furthermore, a laboratory-grade drain modulator circuit with current sensing is proposed, being re-configurable for both Gallium Nitride (GaN) and Gallium Arsenide (GaAs) voltage ranges. Modulated measurements with a 500 MHz bandwidth have been performed on a two-way power-combined Doherty PA designed in 22 nm FD-SOI, resulting in an improvement of the Adjacent Channel Power Ratio (ACPR) of 10.7 dB and an improvement of the RMS Error Vector Magnitude (EVM) of 8.5% after DPD.