NEWS
Nov 11, 2022
PUBLICATIONS

Mechanism of Capacitive Coupling of Proximal Electromagnetic Sources with Biological Bodies

Andreas Christ, Arya Fallahi, Esra Neufeld, Quirino Balzano, and Niels Kuster, Bioelectromagnetics 2022, Volume 43, Issue 7, pp. 404-412, online 06 November 2022; doi: 10.1002/bem.22422

In this study, we investigate the absorption of the electric (E-) field induced in homogeneous biological tissue exposed to highly localized field sources, such as the charged tips of antennas, in proximity to the body, where E-field coupling dominates. These conditions are relevant for compliance testing of modern mobile phones, for which exposure is evaluated under conditions of a small separation between the radiator and the body. We derive an approximation that characterizes the decay of the induced E-field in the tissue as a function of distance. The absorption is quantified in terms of the local specific absorption rate (SAR) at the tissue surface as a function of the charge at the antenna tip. The approximation is based on the analytical evaluation of the E-fields of a charged disk under quasi-static conditions. We validate this approximation using full-wave simulations of dipoles. We demonstrate that the coupling mechanism of the E-field is dominated by the perpendicular field component, and that wave propagation need not be considered for the characterization of the exposure. The surface SAR decreases approximately with the 4th power of the distance and with the square of the ratio of the permittivities of the tissue and free-space. The approximation allows the induced maximum E-field to be predicted with an accuracy of better than 1.5 dB.

The scientific and technical impact of the study can be summarized as:

  • Capacitive coupling is dominant for electrically small antenna elements located close to the exposed tissue, whereas inductive coupling dominates at distances of a few millimeters or more
  • The attenuation of the capacitively coupled E-fields in the tissue reaches the 4th power of the distance and is significantly higher than that of inductive coupling
  • In the tissue, the amplitude of the perpendicular incident E-field is reduced by up to 60 dB in the extremely low frequency range because of the large contrast in dielectric properties of the tissue compared to free space
  • For applications operating in the low MHz range, such as wireless chargers, exposure due to capacitive coupling is negligible due to the high dielectric contrast, and inductive coupling is dominant
PUBLICATIONS

Feb 1, 2003

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nk@itis.swiss

 

Effect of the Meniscus at the Solid/Liquid Interface on the SAR Distribution in Petri Dishes and Flasks

Jürgen Schuderer and Niels Kuster, Bioelectromagnetics, Volume 24, Issue 2, pp. 103–108, February 2003

 

 
PUBLICATIONS

Dec 1, 2002

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nk@itis.swiss

 

Correction of Numerical Phase Velocity Errors in Nonuniform FDTD Meshes

Andreas Christ, Jürg Fröhlich, and Niels Kuster, IEICE Transactions on Communications, Volume E85-B, Issue 12, pp. 2904–2915, December 2002

 

 
PUBLICATIONS

Dec 1, 2002

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nk@itis.swiss

 

Towards Danger of Mobile Phones in Planes, Trains, Cars and Elevators

Axel Kramer, Jürg Fröhlich and Niels Kuster, Journal of the Physical Society of Japan, Volume 71, Issue 12, page 3100, December 2002

 

 
PUBLICATIONS

Dec 1, 2002

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nk@itis.swiss

 

Electromagnetic Fields, Such as Those from Mobile Phones, Alter Regional Cerebral Blood Flow and Sleep and Waking EEG

R. Huber, V. Treyer, A.A. Borbély, J. Schuderer, J.M. Gottselig, H.-P. Landolt, E. Werth, T. Bertholod, N. Kuster, A. Buck, and P. Achermann, Journal of Sleep Research, Volume 11 Issue 4, pp. 289–295, December 2002

 

 
PUBLICATIONS

Apr 4, 2002

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nk@itis.swiss

 

Chavannes (2002) Thesis

Nicolas P. Chavannes, “Local Mesh Refinement Algorithms for Enhanced Modeling Capabilities in the FDTD Method,” PhD Thesis, Swiss Federal Insititute of Technology, Thesis No. 14577, Zurich, 2002

 

 
PUBLICATIONS

Dec 3, 2001

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nk@itis.swiss

 

Basis for Optimization of In Vitro Exposure Apparatus for Health Hazard Evaluations of mObile Communications

Frank Schönborn, Katja Pokovic, Michael Burkhardt, and Niels Kuster, Bioelectromagnetics, Volume 22, Issue 8, pp. 547–559, December 2001

 

 
PUBLICATIONS

Dec 1, 2001

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nk@itis.swiss

 

Review of Dosimetry and Near-field Measurement Techniques for Human Exposure Evaluations and Bioexperiments

Niels Kuster, “Review of dosimetry and near-field measurement techniques for human exposure evaluations and bioexperiments,” in Communication Mobile-Effects Biologique, Claude Legris, CADAS, Acadèmie des Sciences, Paris, France, 2001

 

 
PUBLICATIONS

Oct 1, 2001

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nk@itis.swiss

 

 
PUBLICATIONS

Dec 1, 2000

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nk@itis.swiss

 

Experimental and Numerical Near-Field Evaluation of RF Transmitters

Katja Pokovic, Michael Burkhardt, and Niels Kuster, in Radio Frequency Radiation Dosimetry, Kluwer Academic Publishers, The Netherlands, 2000

 

 
PUBLICATIONS

Nov 1, 2000

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nk@itis.swiss

 

Appropriate Modeling of the Ear for Compliance Testing of Handheld MTE with SAR Safety Limits at 900/1800 MHz

Michael Burkhardt and Niels Kuster, IEEE Transactions on Microwave Theory and Techniques, Volume 48, Issue 11 (Part 1), pp. 1927–1934, November 2000

 

 
PUBLICATIONS

Nov 1, 2000

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nk@itis.swiss

 

The Dependence of Electromagnetic Energy Absorption upon Human Head Tissue Composition in the Frequency Range of 300–3000 MHz

Antonios Drossos, Veli Santomaa, and Niels Kuster, IEEE Transactions on Microwave Theory and Techniques, Volume 48, Issue 11 (Part 2), pp. 1988–1995, November 2000

 

 
PUBLICATIONS

Oct 1, 2000

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nk@itis.swiss

 

Exposure to Pulsed High-frequency Electromagnetic Field During Waking Affects Human Sleep EEG

Reto Huber, Thomas Graf, Kimberly A. Cote, Lutz Wittmann, Eva Gallmann, Daniel Matter, Jürgen Schuderer, Niels Kuster, Alexander A. Borbély, and Peter Achermann, NeuroReport, Volume 11, Issue 15, pp. 3321–3325, October 2000

 

 
PUBLICATIONS

Aug 1, 2000

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nk@itis.swiss

 

Millimeter-Resolution E-field Probe for Isotropic Measurement in Lossy Media Between 100 MHz and 20 GHz

Katja Pokovic, Thomas Schmid, and Niels Kuster, IEEE Transactions on Instrumentation and Measurement, Volume 49, Issue 4, pp. 873–878, August 2000

 

 
PUBLICATIONS

Aug 1, 2000

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nk@itis.swiss

 

Electromagnetic and Heat Transfer Computations for Non-ionizing Radiation Dosimetry

Theodoros Samaras, Peter Regli, and Niels Kuster, Physics in Medicine and Biology, Volume 45, Issue 8, pp. 2233–2246, August 2000

 

 
PUBLICATIONS

Jul 1, 2000

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nk@itis.swiss

 

Design, Optimization, Realization, and Analysis of an In Vitro System for the Exposure of Embryonic Stem Cells at 1.71 GHz

Frank Schönborn, Katja Pokovic, Anna M. Wobus, and Niels Kuster, Bioelectromagnetics, Volume 21, Issue 5, pp. 372–384, July 2000

 

 
PUBLICATIONS

Jun 1, 2000

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nk@itis.swiss

 

Analysis of EEG Data from Weak-field Magnetic Stimulation of Mesial Temporal Lobe Epilepsy Patients

Jon Dobson, Timothy G. St. Pierre, Paola P. Schultheiss-Grassi, H. Gregor Wieser, and Niels Kuster, Brain Research, Volume 868, Issue 2, pp. 386–391, June 2000

 

 
PUBLICATIONS

May 1, 2000

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nk@itis.swiss

 

 
PUBLICATIONS

May 1, 2000

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nk@itis.swiss

 

Novel Probes and Evaluation Procedures to Assess Field Magnitude and Polarization

Katja Pokovic, Thomas Schmid, Jürg Fröhlich, and Niels Kuster, IEEE Transactions on Electromagnetic Compatibility, Volume 42, Issue 2, pp. 240–244, May 2000

 

 
PUBLICATIONS

Apr 13, 2000

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nk@itis.swiss

 

Review of FDTD Time-Stepping Schemes for Efficient Simulation of Electric Conductive Media

Christian Schuster, Andreas Christ, and Wolfgang Fichtner, Microwave and Optical Technology Letters, Volume 25, Issue 1, pp. 16–21, April 2000

 

 
PUBLICATIONS

Apr 12, 2000

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nk@itis.swiss

 

Spontaneous and Nitrosourea-Induced Primary Tumors of the Central Nervous System in Fischer 344 Rats Exposed to Frequency-modulated Microwave Fields

W. Ross Adey, Craig V. Buys, Robert J. Higgins, Robert A. Jones, Charles J. Kean, Niels Kuster, Anne MacMurray, Robert B. Stagg, and Grenith Zimmermann, Journal of Cancer Research, Volume 60, April 2000

 

 
PUBLICATIONS

Apr 4, 2000

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nk@itis.swiss

 

Schönborn (2000) Thesis

Frank J. Schönborn, “Risk Assessment to EMF Exposure ,” PhD Thesis, Swiss Federal Insititute of Technology, Thesis No. 13839, Zurich, 2000

 

 
PUBLICATIONS

Dec 1, 1999

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nk@itis.swiss

 

Review of Exposure Assessment for Handheld Mobile Communications, Devices and Antenna Studies for Optimized Performance

Michael Burkhardt and Niels Kuster, in Review of Radio Science 1996-1999, W.R. Stone, Ed., Oxford University Press, 1999

 

 
PUBLICATIONS

Dec 1, 1999

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nk@itis.swiss

 

Antenna Near-field Evaluations and Compliance Tests with Safety Standards

Niels Kuster, in Mobile Antenna Systems Handbook, K. Fujimoto and J. R. James, Eds. Artech House Publisher, Boston / London, second edition, 1999

 

 
PUBLICATIONS

Sep 1, 1999

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nk@itis.swiss

 

Spontaneous and Nitrosourea-Induced Primary Tumors of the Central Nervous System in Fischer 344 Rats Chronically Exposed to 836 MHz Modulated Microwaves

W. R. Adey, C. V. Buys, R. J. Higgins, R. A. Jones, C. J. Kean, N. Kuster, A. MacMurray, R. B. Stagg, G. Zimmermann, J. L. Phillips, and W. Haggren, Journal of Radiation Research, Volume 152, Issue 3, pp. 293–302, September 1999

 

 
AWARDS

Jun 22, 1999

 

Curtis Carl Johnson Memorial Award for First Place Poster (1999)

Katja Pokovic won the first place student award at the 1999 meeting of the Bioelectromagnetics Society (BEMS1999), in Long Beach, California, USA

 
PUBLICATIONS

Apr 4, 1999

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nk@itis.swiss

 

Burkhardt (1999) Thesis

Michael Burkhardt, “Contributions toward Uncertainty Assessments and Error Minimization of FDTD Simulations Involving Complex Dielectric ,” PhD Thesis, Swiss Federal Insititute of Technology, Thesis No. 13176, Zurich, 1999

 

 
PUBLICATIONS

Apr 4, 1999

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nk@itis.swiss

 

Pokovic (1999) Thesis

Katja Pokovic, “Advanced Electromagnetic Probes for ,” PhD Thesis, Swiss Federal Insititute of Technology, Thesis No. 13334, Zurich, 1999

 

 
PUBLICATIONS

Dec 1, 1998

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nk@itis.swiss

 

Compliance Testing of Hand-held Mobile Communications Equipment

Niels Kuster, in Wireless Phones and Health, George L. Carlo, Ed., Kluwer Academic Publishers, Boston / Dordrecht / London, November 1998

 

 
PUBLICATIONS

Nov 30, 1998

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nk@itis.swiss

 

Comparison Between Numerical and Experimental Near-field Evaluation of a DCS1800 Mobile Telephone

Achim Bahr, Ralf Käastle, Sheng-Gen Pan, Thomas Schmid, Thomas Becks, and Niels Kuster, Radio Science, Volume 33, Issue 6, pp. 1553–1563, November-December 1998

 

 
PUBLICATIONS

Aug 20, 1998

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nk@itis.swiss

 

Miniature Dielectric-Loaded Personal Telephone Antennas with Low User Exposure

Oliver Leisten, Y. Vardaxoglou, Thomas Schmid, B. Rosenberger, E. Agboraw, Niels Kuster, and G. Nicolaidis, Electronics Letters (IEEE), Volume 34, Issue 17, pp. 1628–1629, August 1998

 

 
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