New Real-Time Pulsed-RF NVNA Testbed for Isothermal Characterization of Traps in GaN HEMTs

This paper presents an oscilloscope-based nonlinear vector network analyzer (NVNA) capable of capturing real-time measurements of pulsed large-signal excitations of nonlinear two-port devices. A methodology for the NVNA calibration is presented with the necessary equations to reconstruct the time-domain waveforms at the device-under-test (DUT) port from the waveforms measured at the coupler outputs. The harmonic phase reference and power calibrations are performed jointly using a calibrated Keysight PNA-X in NVNA mode. An example measurement of successive pulsed active loadpull excitations of a GaN HEMT biased for Class A operation captured with the real-time NVNA is presented, demonstrating the capability and sensitivity of the instrument to capture nuanced operation of the device that is unable to be measured by contemporary NVNAs.