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Electromagnetic pulsed‐wave radiation in spherical models of dispersive biological substances
Author(s) -
Moten Krishnan,
Durney Carl H.,
Stockham Thomas G.
Publication year - 1991
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/bem.2250120602
Subject(s) - wavelength , optics , harmonics , radius , plane wave , spherical harmonics , pulse (music) , absorption (acoustics) , electromagnetic radiation , spheres , physics , fourier series , dielectric , fourier transform , materials science , field (mathematics) , pulse wave , computational physics , optoelectronics , laser , mathematics , mathematical analysis , computer security , quantum mechanics , voltage , astronomy , detector , computer science , pure mathematics
In analytical studies, we investigated induced‐field patterns and SAR distributions in a lossy, dispersive, homogeneous, dielectric sphere typical of muscle tissue as irradiated by a plane‐wave pulse train consisting of a pulse‐modulated sinusoidal carrier wave. Calculations were made for carrier frequencies of 1, 3, and 15 GHz, pulse widths of 0.333, 2.0 and 4 ns, and pulse repetition rates of 1.11 × 10 6 , 100 × 10 6 , and 181.18 × 10 6 pps. The classical Mie solution was modified for a train of incident pulses that was represented by a Fourier series, and the fast‐Fourier transform was used to sum the series. Computationally, the technique proved to be feasible and less expensive than we expected. The calculated field patterns show that the sphere's physical dimensions and the internal wavelength of the carrier greatly influence the nature of pulse‐train propagation in the sphere. Harmonics having internal wavelengths nearly equal to the radius of the sphere produce most of the absorption; other harmonics produce little absorption. An intense hot spot is observed in spheres with radii that match the carriers' wavelengths.