A communication device, such as a smart phone, includes an envelope tracking power supply modulator. The envelope tracking power supply modulator receives an envelope tracking reference signal. A baseband controller pre-distorts the envelope tracking reference signal responsive to distortion caused by the envelope tracking power supply modulator. For instance, the pre-distortion may modify the nominal envelope tracking reference signal so that, after the modulator acts on the modified reference signal, the output of the modulator has increased linearity.