Impacto del autocalentamiento en la linealización de un transmisor polar basado en un amplificador a GaN HEMT

Abstract

In this paper, the impact of self heating on the linearity of a polar transmitter, with a saturated GaN HEMT switched mode power amplifier (PA) as final RF stage, is studied. The thermal circuit parameters of a commercial GaN HEMT device were extracted in order to evaluate the temperature rise dependence on power dissipation. A temperature dependent characterization of the PA modulation profiles was realized and its behaviour under two tone excitations with different frequency spacing was obtained through measurements and simulations, being the self heating effects clearly masked by other nonidealities, as the case of feedthrough. In this sense, linearization techniques as memoryless digital predistortion and I/Q vector hole punching were applied to the two tone excitation with the aim of extracting the real self heating contribution. Finally, temperature dynamics influence on the system residual distortion under a real communication signal excitation is shown.