  In this paper, we provide a novel framework for efficient digital
predistortion (DPD) based linearization of active antenna arrays with multiple
and mutually different nonlinear power amplifiers. The proposed method builds
on the use of a combined feedback signal essentially characterizing the
observable nonlinear distortion at the receiving end. The proposed method is
validated with extensive over-the-air RF measurements on a 64-element active
antenna array transmitter operating at 28 GHz carrier frequency and
transmitting a 200 MHz wide 5G New Radio (NR) waveform. The obtained results
demonstrate the excellent linearization capabilities of the proposed solution,
which allows for a very efficient implementation in practical systems.
