Implementation issues in FPGA-controlled polar transmitters

This paper presents a digital platform to generate, linearize and adjust complex baseband and intermediate frequency signals for operating in both envelope tracking and polar transmitters. The closed-loop nature of this field programmable gate array (FPGA)-based set-up allows introducing control strategies to overcome or mitigate some of the unwanted distortion arising from maladjustments in the aforementioned efficient transmitters. Real-time adaptive digital predistortion is also provided to improve the overall linearity of the system. In a first approach, memoryless predistortion has been considered; however, additional look-up-tables can be easily included to compensate for memory effects.