Radio transmitter and method therefor

A method performed by a processing device for use in a radio transmitter, wherein the radio transmitter comprises a first power amplifier (PA) corresponding to a first antenna port, an observation receiver configured to process an output from the first PA to feed back an observation signal, and one or more second PA each corresponding to a second antenna port, the method comprising:

• determining a first function reflecting a nonlinearity of the first PA, based on a first input signal to the first PA, the observation signal and a first set of parameters characterizing the first PA;
• determining a first pre-distortion and applying the first pre-distortion to a first baseband signal for the first antenna port;
• determining, for each of the one or more second PA, a second function reflecting a nonlinearity of the second PA, based on the first function and a difference between a second set of parameters characterizing the second PA and the first set of parameters;
• and
• determining, for the second PA, a second pre-distortion based on the second function and applying the second pre-distortion to a second baseband signal for the second antenna port.

A processing device for use in a radio transmitter, wherein the radio transmitter comprises a first power amplifier (PA) corresponding to a first antenna port, an observation receiver configured to process an output from the first PA to feed back an observation signal, and one or more second PA each corresponding to a second antenna port, the processing device comprising:

• at least one processor;
• and
• at least one memory, the at least one memory containing instructions executable by the at least one processor, whereby the processing device is operative to:
• determine a first function reflecting a nonlinearity of the first PA, based on a first input signal to the first PA, the observation signal and a first set of parameters characterizing the first PA;
• determine a first pre-distortion and apply the first pre-distortion to a first baseband signal for the first antenna port;
• determine, for each of the one or more second PA, a second function reflecting a nonlinearity of the second PA, based on the first function and a difference between a second set of parameters characterizing the second PA and the first set of parameters;
• and
• determine, for the second PA, a second pre-distortion based on the second function and apply the second pre-distortion to a second baseband signal for the second antenna port.