Off-axis second-order high-TC rf SQUID gradiometer for magnetocardiography in unshielded environment

Hong Chang Yang; Shu Yun Wang; Jen Tzong Jeng; Jau Han Chen; Herng Er Horng

doi:10.1109/TASC.2003.813853

Off-axis second-order high-T_C rf SQUID gradiometer for magnetocardiography in unshielded environment

Hong Chang Yang^*, Shu Yun Wang, Jen Tzong Jeng, Jau Han Chen, Herng Er Horng

^*Corresponding author for this work

Research output: Contribution to journal › Conference article › peer-review

Abstract

We study an electronic gradiometer system for magnetocardiography (MCG) in unshielded environments. The electronically balanced gradiometer consists of three high temperature radio-frequency (rf) superconducting quantum interference device (SQUID) magnetometers, arranged in off-axis arrangement with the baseline of 6 cm to form the second order (2nd-order) gradiometer system. A set of coefficients were found to optimize the noise spectrum of the 2nd-order gradiometer via the fast Fourier transform technique by considering both the phase and the amplitude in the subtraction circuit. Besides, the signal of the 2nd-order gradiometer was filtered by notch and low frequency band pass filters. Hence, the field noise spectrum of the 2nd-order gradiometer was reduced to 1.5 pT/Hz^1/2 at 60 Hz, to 1 pT/Hz^1/2 at 10 Hz, and to 1.5 pT/Hz^1/2 at 1 Hz. We perform MCG measurements in unshielded environments. To enhance the signal to noise ratio, the measured MCG signals were averaged according to the simultaneously recorded electrocardiogram signals recorded simultaneously. The MCG measurement was performed over several locations above the thorax of a human being. Our results demonstrate that the off-axis arrangement can offer the flexibility in the design of the SQUID-based multichannel magnetocardiogram.

Original language	English
Pages (from-to)	360-363
Number of pages	4
Journal	IEEE Transactions on Applied Superconductivity
Volume	13
Issue number	2 I
DOIs	https://doi.org/10.1109/TASC.2003.813853
Publication status	Published - 2003 Jun
Externally published	Yes
Event	2002 Applied Superconductivity Conference - Houston, TX, United States Duration: 2002 Aug 4 → 2002 Aug 9

Keywords

Gradiometers
Magnetocardiography
SQUID's

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics
Electrical and Electronic Engineering

Access to Document

10.1109/TASC.2003.813853

Cite this

@article{c63123bb7d3d4b518d9df9b1955cb425,

title = "Off-axis second-order high-TC rf SQUID gradiometer for magnetocardiography in unshielded environment",

abstract = "We study an electronic gradiometer system for magnetocardiography (MCG) in unshielded environments. The electronically balanced gradiometer consists of three high temperature radio-frequency (rf) superconducting quantum interference device (SQUID) magnetometers, arranged in off-axis arrangement with the baseline of 6 cm to form the second order (2nd-order) gradiometer system. A set of coefficients were found to optimize the noise spectrum of the 2nd-order gradiometer via the fast Fourier transform technique by considering both the phase and the amplitude in the subtraction circuit. Besides, the signal of the 2nd-order gradiometer was filtered by notch and low frequency band pass filters. Hence, the field noise spectrum of the 2nd-order gradiometer was reduced to 1.5 pT/Hz1/2 at 60 Hz, to 1 pT/Hz1/2 at 10 Hz, and to 1.5 pT/Hz1/2 at 1 Hz. We perform MCG measurements in unshielded environments. To enhance the signal to noise ratio, the measured MCG signals were averaged according to the simultaneously recorded electrocardiogram signals recorded simultaneously. The MCG measurement was performed over several locations above the thorax of a human being. Our results demonstrate that the off-axis arrangement can offer the flexibility in the design of the SQUID-based multichannel magnetocardiogram.",

keywords = "Gradiometers, Magnetocardiography, SQUID's",

author = "Yang, {Hong Chang} and Wang, {Shu Yun} and Jeng, {Jen Tzong} and Chen, {Jau Han} and Horng, {Herng Er}",

note = "Funding Information: Manuscript received August 5, 2002. This work was supported by the Ministry of Education of the R.O.C. under the program of promoting university academic excellence 91-N-FA01-2-4. H.-C. Yang, S.-Y. Wang, J.-T. Jeng, and J.-H. Chen are with the Department of Physics, National Taiwan University, Taipei 10617, Taiwan, R.O.C. (e-mail: hcyang@phys.ntu.edu.tw). H.-E. Horng is with the Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan, R.O.C. Digital Object Identifier 10.1109/TASC.2003.813853; 2002 Applied Superconductivity Conference ; Conference date: 04-08-2002 Through 09-08-2002",

year = "2003",

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T1 - Off-axis second-order high-TC rf SQUID gradiometer for magnetocardiography in unshielded environment

AU - Yang, Hong Chang

AU - Wang, Shu Yun

AU - Jeng, Jen Tzong

AU - Chen, Jau Han

AU - Horng, Herng Er

N1 - Funding Information: Manuscript received August 5, 2002. This work was supported by the Ministry of Education of the R.O.C. under the program of promoting university academic excellence 91-N-FA01-2-4. H.-C. Yang, S.-Y. Wang, J.-T. Jeng, and J.-H. Chen are with the Department of Physics, National Taiwan University, Taipei 10617, Taiwan, R.O.C. (e-mail: hcyang@phys.ntu.edu.tw). H.-E. Horng is with the Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan, R.O.C. Digital Object Identifier 10.1109/TASC.2003.813853

PY - 2003/6

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N2 - We study an electronic gradiometer system for magnetocardiography (MCG) in unshielded environments. The electronically balanced gradiometer consists of three high temperature radio-frequency (rf) superconducting quantum interference device (SQUID) magnetometers, arranged in off-axis arrangement with the baseline of 6 cm to form the second order (2nd-order) gradiometer system. A set of coefficients were found to optimize the noise spectrum of the 2nd-order gradiometer via the fast Fourier transform technique by considering both the phase and the amplitude in the subtraction circuit. Besides, the signal of the 2nd-order gradiometer was filtered by notch and low frequency band pass filters. Hence, the field noise spectrum of the 2nd-order gradiometer was reduced to 1.5 pT/Hz1/2 at 60 Hz, to 1 pT/Hz1/2 at 10 Hz, and to 1.5 pT/Hz1/2 at 1 Hz. We perform MCG measurements in unshielded environments. To enhance the signal to noise ratio, the measured MCG signals were averaged according to the simultaneously recorded electrocardiogram signals recorded simultaneously. The MCG measurement was performed over several locations above the thorax of a human being. Our results demonstrate that the off-axis arrangement can offer the flexibility in the design of the SQUID-based multichannel magnetocardiogram.

AB - We study an electronic gradiometer system for magnetocardiography (MCG) in unshielded environments. The electronically balanced gradiometer consists of three high temperature radio-frequency (rf) superconducting quantum interference device (SQUID) magnetometers, arranged in off-axis arrangement with the baseline of 6 cm to form the second order (2nd-order) gradiometer system. A set of coefficients were found to optimize the noise spectrum of the 2nd-order gradiometer via the fast Fourier transform technique by considering both the phase and the amplitude in the subtraction circuit. Besides, the signal of the 2nd-order gradiometer was filtered by notch and low frequency band pass filters. Hence, the field noise spectrum of the 2nd-order gradiometer was reduced to 1.5 pT/Hz1/2 at 60 Hz, to 1 pT/Hz1/2 at 10 Hz, and to 1.5 pT/Hz1/2 at 1 Hz. We perform MCG measurements in unshielded environments. To enhance the signal to noise ratio, the measured MCG signals were averaged according to the simultaneously recorded electrocardiogram signals recorded simultaneously. The MCG measurement was performed over several locations above the thorax of a human being. Our results demonstrate that the off-axis arrangement can offer the flexibility in the design of the SQUID-based multichannel magnetocardiogram.

KW - Gradiometers

KW - Magnetocardiography

KW - SQUID's

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JO - IEEE Transactions on Applied Superconductivity

JF - IEEE Transactions on Applied Superconductivity

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