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Sensor Configuration and Algorithms for Power-Line Interference Suppression in Low Field Nuclear Magnetic Resonance

1,2,3,4,5, 1,2,4,*, 1,2,4, 1,2,4,5, 1,2,4,5, 1,2,4, 3,4,*, 3,4 and 1,2,4
1
State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050, China
2
CAS Center for ExcelleNce in Superconducting Electronics (CENSE), Shanghai 200050, China
3
Institute of Complex System (ICS-8), Forschungszentrum Jülich (FZJ), D-52425 Jülich, Germany
4
Joint Research Institute on Functional Materials and Electronics, Collaboration between SIMIT and FZJ, D-52425 Jülich, Germany
5
University of Chinese Academy of Sciences, Beijing 100049, China
*
Authors to whom correspondence should be addressed.
Sensors 2019, 19(16), 3566; https://doi.org/10.3390/s19163566
Received: 21 July 2019 / Revised: 12 August 2019 / Accepted: 14 August 2019 / Published: 15 August 2019
(This article belongs to the Section Physical Sensors)
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Abstract

Low field (LF) nuclear magnetic resonance (NMR) shows potential advantages to study pure heteronuclear J-coupling and observe the fine structure of matter. Power-line harmonics interferences and fixed-frequency noise peaks might introduce discrete noise peaks into the LF-NMR spectrum in an open environment or in a conductively shielded room, which might disturb J-coupling spectra of matter recorded at LF. In this paper, we describe a multi-channel sensor configuration of superconducting quantum interference devices, and measure the multiple peaks of the 2,2,2-trifluoroethanol J-coupling spectrum. For the case of low signal to noise ratio (SNR) < 1, we suggest two noise suppression algorithms using discrete wavelet analysis (DWA), combined with either least squares method (LSM) or gradient descent (GD). The de-noising methods are based on spatial correlation of the interferences among the superconducting sensors, and are experimentally demonstrated. The DWA-LSM algorithm shows a significant effect in the noise reduction and recovers SNR > 1 for most of the signal peaks. The DWA-GD algorithm improves the SNR further, but takes more computational time. Depending on whether the accuracy or the speed of the de-noising process is more important in LF-NMR applications, the choice of algorithm should be made. View Full-Text
Keywords: ultra-low field; nuclear magnetic resonance; superconducting quantum interference device; de-noising algorithms; power-line harmonics interference; J-coupling ultra-low field; nuclear magnetic resonance; superconducting quantum interference device; de-noising algorithms; power-line harmonics interference; J-coupling
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Huang, X.; Dong, H.; Tao, Q.; Yu, M.; Li, Y.; Rong, L.; Krause, H.-J.; Offenhäusser, A.; Xie, X. Sensor Configuration and Algorithms for Power-Line Interference Suppression in Low Field Nuclear Magnetic Resonance. Sensors 2019, 19, 3566.

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