Recent Advances in Power Encoding and GaN Switching Technologies for Digital Transmitters

Green and flexible digital transmitter is envisioned as the evolving trend for future cellular base station, which is required to operate with multi-standard and multi-band radio signals. To energy efficiently amplify the spectrum-efficient modulated signals with high peak-to-average power ratio (PAPR>10 dB) is challenging. Compared with traditional analog solutions using Doherty Power Amplifier (DPA) or Envelope Tracking (ET), switch-mode digital power amplifier (e.g. class-S PA) in digital transmitter is offering good agility as well as theoretically 100% efficiency thanks to its unique operation principles.
In recent years, numerous researches on the enabling technologies of digital transmitter have been reported. It includes advanced power encoding schemes to generate the optimized switching signals. Gallium nitride (GaN) transistor technologies have been considered as an ideal candidate for implementing power switching stage of class-S PA. This paper will review these key topics for digital transmitter with design challenges and potential approaches.