Distortion and impairments mitigation and compensation of single- and multi-band wireless transmitters (invited)

Transmitter digital domain linearisation solutions are constantly evolving to extract optimum benefits in terms of cost, performance and flexibility. This study highlights the current and futuristic trends in the arena of transmitter system modelling and digital domain compensation for radio frequency distortions of non-linear power amplifiers and wireless transmitters in case of single-band wireless transmitter, which is further extended to a dual-band transmitter. Indeed, the dual-band transmitter results in severe non-linear distortion as compared to the single-band transmitter when operated in concurrent mode, due to the additional inter-modulation products generated by the dual-band transmitted signals. Hence, in addition to the intermodulation products and memory effects exhibited in a single-band transmitter, the cross-modulation effects of the dual-band signals should be compensated for as well in a dual-band transmitter. The effects of the modulator imperfections such as gain and phase imbalances, phase errors and DC offsets and their impact on the feedback loop of a digital predistortion system are also analysed. A thorough comparison between the state-of-the-art behavioural models and their application to digital predistortion technique of power amplifier is presented in terms of performance and complexity. Model performance assessment is discussed through simulation and experimental results for both single- and dual-band systems.