Digital predistortion for envelope tracking power amplifiers

Envelope tracking seeks to achieve an optimally efficient PA by modulating the supply voltage and operating the RFPA at peak instantaneous efficiency over the majority of the waveform. However, it implies using a second power amplifier, the envelope amplifier (or envelope modulator) and it results in a nonlinear “mixing” process between the RF signal and the supply voltage. By using digital predistortion, it is possible to compensate for the system nonlinearity and achieve the desired transmitted signal. This talk will provide insights into envelope tracking systems and focus on improvements in digital predistortion beyond that used on systems with constant supply PA's.