Abstract: A radio transmitter and a method therefor are disclosed. According to an embodiment, the radio transmitter comprises a first power amplifier (PA) corresponding to a first antenna port, an observation receiver, a first determination module, a first pre-distortion module, one or more second PA each corresponding to a second antenna port, one or more second determination module and one or more second pre-distortion module. The first determination module is configured to determine a first function reflecting a nonlinearity of the first PA, based on a first input signal to the first PA, an observation signal from the observation receiver and a first set of parameters characterizing the first PA. The first pre-distortion module is configured to determine and apply a first pre-distortion to a first baseband signal for the first antenna port.