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Widely-linear beamforming and RF impairment suppression in massive antenna arrays
Journal article   Open access

Widely-linear beamforming and RF impairment suppression in massive antenna arrays

Aki Hakkarainen, Janis Werner, Kapil R Dandekar and Mikko Valkama
Journal of communications and networks, v 15(4), pp 383-397
Aug 2013
url
https://doi.org/10.1109/JCN.2013.000069View
Published, Version of Record (VoR) Open

Abstract

Radio frequency Array signal processing beam steering in-phase quadrature-phase (I/Q) imbalance radio transceivers Interference circular signals MIMO Vectors massive multiple input multiple output (MIMO) Antenna arrays Antenna radiation patterns
In this paper, the sensitivity of massive antenna arrays and digital beamforming to radio frequency (RF) chain in-phase quadrature-phase (I/Q) imbalance is studied and analyzed. The analysis shows that massive antenna arrays are increasingly sensitive to such RF chain imperfections, corrupting heavily the radiation pattern and beamforming capabilities. Motivated by this, novel RF-aware digital beamforming methods are then developed for automatically suppressing the unwanted effects of the RF I/Q imbalance without separate calibration loops in all individual receiver branches. More specifically, the paper covers closed-form analysis for signal processing properties as well as the associated radiation and beamforming properties of massive antenna arrays under both systematic and random RF I/Q imbalances. All analysis and derivations in this paper assume ideal signals to be circular. The well-known minimum variance distortionless response (MVDR) beamformer and a widely-linear (WL) extension of it, called WL-MVDR, are analyzed in detail from the RF imperfection perspective, in terms of interference attenuation and beamsteering. The optimum RF-aware WL-MVDR beamforming solution is formulated and shown to efficiently suppress the RF imperfections. Based on the obtained results, the developed solutions and in particular the RF-aware WL-MVDR method can provide efficient beamsteering and interference suppressing characteristics, despite of the imperfections in the RF circuits. This is seen critical especially in the massive antenna array context where the cost-efficiency of individual RF chains is emphasized.

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Collaboration types
Domestic collaboration
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Web of Science research areas
Computer Science, Information Systems
Telecommunications
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