Interference Mitigation by Adaptive Analog Spatial Filtering for MIMO Receivers

Exposed to strong cochannel/adjacent-channel interference, digital multiple-input-multiple-output (MIMO) receivers require high-dynamic-range analog-to-digital converters (ADCs). Hybrid beamforming featuring spatial filtering before the ADCs can adaptively mitigate interference in both the analog an...

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Bibliographic Details
Published in:IEEE transactions on microwave theory and techniques 2021-09, Vol.69 (9), p.4169-4179
Main Authors: Alaei, Masoud Abbasi, Golabighezelahmad, Sajad, de Boer, Pieter-Tjerk, van Vliet, Frank E., Klumperink, Eric A. M., Kokkeler, Andre B. J.
Format: Article
Language:English
Subjects:
Adaptive algorithms
Adaptive spatial filtering
Analog to digital conversion
Analog to digital converters
Antenna arrays
Antenna measurements
Array signal processing
Beamforming
CMOS
Computer architecture
Constellations
Dipole antennas
hybrid beamforming
Interference
interference rejection
MIMO communication
multiple-input–multiple-output (MIMO)
Mutual coupling
Optimization
Radio frequency
receiver
Receivers
Receivers & amplifiers
software-defined radio
Spatial filtering
vector modulator (VM)
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Summary:Exposed to strong cochannel/adjacent-channel interference, digital multiple-input-multiple-output (MIMO) receivers require high-dynamic-range analog-to-digital converters (ADCs). Hybrid beamforming featuring spatial filtering before the ADCs can adaptively mitigate interference in both the analog and digital domains; hence relaxing the required dynamic ranges of the ADCs. This article demonstrates the effectiveness of hybrid beamforming in this mitigation utilizing adaptive minimum mean square error (MMSE) and error vector magnitude (EVM) as an optimization criterion. Extensive EVM measurements are carried out with a conductive setup using a four-element 22-nm FD-SOI CMOS prototype MIMO receiver chip to verify the performance of the adaptive MMSE algorithm. Over-the-air (OTA) measurements with a linear four-element dipole antenna array with half-wavelength spacing in the 2.4-GHz industrial scientific and medical (ISM) band quantify the improvement for real-world scenarios, e.g., having a multipath propagation channel and mutual coupling between the antenna array elements. OTA results show that a rejection of 22.5 and 24.5 dB can be achieved on average in an in-door laboratory environment utilizing vector modulator (VM) constellations with 16 and 64 points, respectively.
ISSN:0018-9480
1557-9670
DOI:10.1109/TMTT.2021.3081110