Digital Predistortion of Phased-Array Transmitter With Shared Feedback and Far-Field Calibration

Digital predistortion (DPD) of a phased array requires that multiple transmit paths must be measured by feedback (FB) receiver (Rx). In this article, we propose an FB concept for DPD in time-division-duplex (TDD) arrays. We use single line to collect the waveform samples from parallel Rx. The TDD switches are used enable and disable individual paths. is calibrated comparing outputs power amplifiers (PAs) over-the-air (OTA) measurement reference performed with frequency-modulated continuous-wave (FMCW) signal. PA measurements postequalized before training model far-field Three alternative strategies considered through compared OTA DPD. performance verified 28-GHz phased-array transmitter fifth-generation new radio terms total radiated adjacent channel ratio (TRACPR), cumulative absolute ACP (CACP), main lobe error vector magnitude (EVM). best EVM ACPR achieved strategy where responses treated independently. methods were comparable performance, achieving all < ?37-dB TRACPR, ?29-dBm/MHz CACP, ?7 % EVM.