A method of compensating envelope tracking nonlinearities in a mobile device, the method comprising: shaping an envelope signal representing an envelope of an input baseband signal (X 1); filtering the shaped envelope signal to limit a bandwidth of the shaped envelope signal to be less than a bandwidth of tracker circuitry of an envelope tracking system of the mobile device in order to obtain a scaled replica (X 2) of an output signal of the tracker circuitry, wherein the tracker circuitry's output signal is provided as a variable voltage power supply to power amplifier, PA, circuitry of transmitter circuitry of the mobile device, the tracker circuitry's output signal being varied by the tracker circuitry according to the scaled replica (X 2) to increase efficiency of the PA circuitry; generating a model distortion signal (X 3) based on the scaled replica (X 2) and the input baseband signal (X 1), the model distortion signal (X 3) emulating envelope tracking linearity degradation of the tracker circuitry; generating an output baseband signal using predistorter circuitry that receives the scaled replica (X 2), the model distortion signal (X 3), and the input baseband signal (X 1) as inputs, wherein the output baseband signal is pre-distorted by the predistorter circuitry relative to the input baseband signal (X 1) according to the scaled replica (X 2), the model distortion signal (X 3), and the input baseband signal (X 1) to compensate for degradations in transmit signal quality due to envelope tracking nonlinearities; and providing the output baseband signal to the transmitter circuitry for conversion to an RF signal for transmission by the transmitter circuitry. shaping an envelope signal representing an envelope of an input baseband signal (X 1); filtering the shaped envelope signal to limit a bandwidth of the shaped envelope signal to be less than a bandwidth of tracker circuitry of an envelope tracking system of the mobile device in order to obtain a scaled replica (X 2) of an output signal of the tracker circuitry, wherein the tracker circuitry's output signal is provided as a variable voltage power supply to power amplifier, PA, circuitry of transmitter circuitry of the mobile device, the tracker circuitry's output signal being varied by the tracker circuitry according to the scaled replica (X 2) to increase efficiency of the PA circuitry; generating a model distortion signal (X 3) based on the scaled replica (X 2) and the input baseband signal (X 1), the model distortion signal (X 3) emulating envelope tracking linearity degradation of the tracker circuitry; generating an output baseband signal using predistorter circuitry that receives the scaled replica (X 2), the model distortion signal (X 3), and the input baseband signal (X 1) as inputs, wherein the output baseband signal is pre-distorted by the predistorter circuitry relative to the input baseband signal (X 1) according to the scaled replica (X 2), the model distortion signal (X 3), and the input baseband signal (X 1) to compensate for degradations in transmit signal quality due to envelope tracking nonlinearities; and providing the output baseband signal to the transmitter circuitry for conversion to an RF signal for transmission by the transmitter circuitry.