Radio station and active antenna array

A method for digitally predistorting a payload signal, the method comprising:

• providing the payload signal to be relayed as a at least two transmit signals along at least two transmit paths,
• imposing a digital predistortion on the payload signal,
• extracting at least two coupled transmit signals out of the at least two transmit signals,
• combining at least two coupled transmit signals, thus forming a common feedback signal,
• updating the digital predistortion of the at least two transmit paths based on extracted distortion information from the common feedback signal;
• thereby linearising a transfer characteristics of at least two of the transmit paths.

Computer program product embodied on a non-transitory computer-readable medium and comprising executable instructions for the manufacture of a radio station, the radio station comprising:

• a digital predistortion module adapted to impose a digital predistortion on a payload signal,
• at least two transmit paths adapted to relay the payload signal as at least two transmit signals,
• an RF amplifier within the at least two transmit paths adapted to amplify the payload signal,
• an antenna element or sub-array terminating the at least two transmit paths,
• a coupler adapted to extract at least two coupled transmit signals out of the at least two transmit signals,
• a combiner adapted to combine the at least two coupled transmit signals into a common feedback signal;
• a common feedback path adapted to feed the common feedback signal to a digital predistortion update module adapted to update the digital predistortion of the at least two transmit paths based on extracted distortion information from the common feedback signal;
• thus linearising transfer characteristics of at least two of the transmit paths.

Non-transitory computer program product comprising instructions that enable a processor to carry out a method for digitally predistorting a payload signal, the method comprising:

• providing the payload signal to be relayed as at least two transmit signals along at least two transmit paths,
• imposing a digital predistortion on the payload signal,
• extracting at least two coupled transmit signals out of the transmit signals,
• combining at least two of the at coupled transmit signals, thus forming a common feedback signal,
• updating the digital predistortion of the at least two transmit paths based on extracted distortion information from the common feedback signal;
• thereby linearising a transfer characteristics of at least two of the transmit paths.

An active antenna array comprising:

• a radio station comprising:
• a digital predistortion module adapted to impose a digital predistortion on a payload signal,
• at least two transmit paths adapted to relay the payload signal as at least two transmit signals,
• an RF amplifier within the at least two transmit paths adapted to amplify the payload signal,
• an antenna element or sub-array terminating the at least two transmit paths,
• a coupler adapted to extract at least two coupled transmit signals out of the transmit signals,
• a combiner adapted to combine the at least two coupled transmit signals into a common feedback signal;
• a common feedback path adapted to feed the common feedback signal to a digital predistortion update module adapted to update the digital predistortion of the at least two transmit paths based on extracted distortion information from the common feedback signal;
• thus linearising transfer characteristics of at least two of the transmit paths;
• wherein the antenna element or sub-array comprises an adjustable phase and magnitude between individual ones of the antenna elements or sub-arrays;
• and
• a signal conditioner adapted to impose phase and magnitude differences between the antenna elements.