An investigation on current collapse induced memory effects of GaN power amplifier for LTE base station applications

This paper discusses for the first time, to the author's knowledge, the impacts of GaN HEMTs current collapse on memory effects of RF power amplifier at back-off power for high PAPR and wide dynamic range applications. Current collapse induced power gain variation of a 3.5GHz 50W class GaN power amplifier is investigated experimentally within the time scale of nano seconds to micro seconds which is comparative with the sampling interval of the digital predistorter for LTE applications. Combined pulsed and continuous CW signal is used to measure RF gain responses at back-off power and the amount of memory effect is estimated numerically. Measured results are compared with AM-AM of LTE modulated signal and indicate that the current collapse is one of dominating factors of the memory effects of the power amplifier at back-off power.