Characterization of memory effects in GaN based HPAs for multi function sensors

Abstract

Truly multi-functional sensor systems are enabled through the recent development of wideband and multi channel digital back ends to control systems with several transmitter and receiver modules, in combination with the advancements in the development of these modules utilizing GaN MMIC based solutions. However, there is a considerable lack of insight into the problem of long term memory effects in broadband GaN MMIC power amplifiers required to enable the next generation of small and lightweight multi functional sensor systems. As such this thesis is focused on the impact of memory effects when changing between two waveforms representative of the different operating conditions applicable for a multi function system. Thus a suitable test bench is designed capable of providing arbitrary waveforms, switching between them and, record the results. The measurement data is modeled in terms of exponential time constants in order to quantify the impact on the behavior of a power amplifier caused by memory effects in terms of amplitude and time. The results indicate the presence of these memory effects in the amplifier operation after switching applications and decrease of influence from the previous waveform as time progress. Furthermore, investigating the effect of timing mismatch between the gate and RF pulsing showed a significant decrease in device performance.