University of Oulu

B. Khan, N. Tervo, M. Jokinen, A. Pärssinen and M. Juntti, "Statistical Digital Predistortion of 5G Millimeter-Wave RF Beamforming Transmitter Under Random Amplitude Variations," in IEEE Transactions on Microwave Theory and Techniques, vol. 70, no. 9, pp. 4284-4296, Sept. 2022,

Statistical digital predistortion of 5G millimeter-wave RF beamforming transmitter under random amplitude variations

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Author: Khan, Bilal1; Tervo, Nuutti1; Jokinen, Markku1;
Organizations: 1Center for Wireless Communications–Radio Technologies (CWC-RT), Faculty of Information Technology and Electrical Engineering (ITEE), University of Oulu, 90570 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.7 MB)
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Language: English
Published: Institute of Electrical and Electronics Engineers, 2022
Publish Date: 2022-10-03


The nonlinearity of the fifth-generation (5G) millimeter-wave (mmWave) phased array transmitter (TX) depends on the variations in the beamforming coefficients, e.g., due to unwanted amplitude errors of the phase shifters or purposely introduced amplitude variations to shape the beam, as well as other analog component variations. Therefore, also the digital predistortion (DPD) coefficients depend on the beamforming coefficients and require a continuous update for different beamsteering directions in a conventional DPD. We propose a robust DPD approach that uses the average array response for DPD training. The average array response is estimated using the known experimental histogram of power amplifier (PA) input power variation resulting from the amplitude variations due to beamforming. The DPD training based on the average array response makes the DPD coefficients insensitive to beamforming variations. The proposed DPD strategy requires a shared feedback path for training and only a single set of DPD coefficients to linearize the array response in all beamsteering directions. The performance of the proposed DPD strategy is validated by over-the-air (OTA) measurements of a 28-GHz phased array TX over different steering angles. Experimental results show that the proposed DPD method using one set of DPD coefficients provides similar linearization performance across the steering angles compared with the DPD trained to all steering angles through the OTA reference antenna.

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Series: IEEE transactions on microwave theory and techniques
ISSN: 0018-9480
ISSN-E: 1557-9670
ISSN-L: 0018-9480
Volume: 70
Issue: 9
Pages: 4284 - 4296
DOI: 10.1109/tmtt.2022.3187129
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: This work was supported in part by the Wireless Connectivity for Internet of Everything Energy Efficient Transceiver and System Design (WiConIE), in part by the Energy-Efficient Radio Access: Methods and Optimization (EERA), and in part by the Academy of Finland 6Genesis Flagship under Grant 318927.
Academy of Finland Grant Number: 318927
Detailed Information: 318927 (Academy of Finland Funding decision)
Copyright information: © The Author(s) 2022. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see