Time-domain measurement system using Track & Hold Amplifier applied to pulsed RF characterization of high power GaN devices

We propose in this paper a time-domain test bench for the pulsed characterization of a high Power GaN Amplifier. Our findings are based on a Track and Hold Amplifier for the down-conversion of RF spectra using the sub harmonic sampling principle. The use of wideband THA to replace samplers or mixers enables reducing component density in an analog domain. It permits direct digitization of entire pulsed RF spectrum, bringing more flexibility in the receiver´s performance by enhancing the dynamics and bandwidth. This test bench is capable of completely extracting the phase, amplitude and pulse profile of the RF signal. Power characteristics, phase and amplitude information for multiple bursts of pulses of a 50 W GaN HEMT Nitronex (NPTB00050B) power amplifier have been measured using the proposed calibrated measurement system. The low frequency memory effects (thermal and trapping) of high power GaN amplifier were also measured.