Error vector magnitude measurement for power amplifiers under wideband load impedance mismatch: System-level analysis and VNA-based implementation

The Error Vector Magnitude (EVM) is a fundamental metric used in communications to quantify the wideband distortion generated by a non-linear device subject to modulated excitation. While typically adopted for impedance-matched devices, the EVM is here investigated for the performance assessment of mismatched power amplifiers (PAs) across wide modulation bandwidths (BWs). A system-level analysis is developed to characterize the EVM for a non-linear device cascaded with a generic linear network. To study particular operating regimes of interest under wideband load mismatch, the EVM measurement process is here applied together with a novel wideband active load-pull technique, leading to a newly implemented frequency-domain characterization platform based on classical relative measurements from a Vector Network Analyzer (VNA). The experimental results ultimately show that the analyzed EVM measurement method can be consistently and effectively combined with load-pull techniques in realistic application cases, enabling improved wideband radio-frequency (RF) PA design and characterization.