On Focusing into a Lossy Medium from a Rectangular Aperture

IEEE Trans. Antennas Propagat.

Wait

2000

Self Cite

In this paper, we are interested in controlling the power dissipation within a homogeneous lossy cylinder of finite length when a field is applied to the surface of the cylinder. The fields are assumed to be independent of the azimuthal angle. To begin, a field which satisfies the required dissipation inside the cylinder is assumed on the axis of the lossy cylinder. An analytical evaluation of the continuous source on the surface of the cylinder can then be carried out. This is an inverse problem where the response is known and the source is to be determined. A realization of the continuous source (surface field) in terms of a discrete array is also given. Results will be presented that show an excellent agreement between the actual continuous sources and the discrete array in producing the field on the axis of the lossy cylinder. In fact, a small number of slots (fifteen or less) produce accurate agreement for the required field on the axis of the cylinder. Bioelectromagnetics and hyperthermia treatment of cancer in cylindrical objects such as limbs and torsos is one potential application. Nondestructive testing of manufactured cylindrical products is another one where the energy is focused in a given region in the cylinder. Index Terms-Absorbing media, biomedical applications of electromagnetic (EM) radiation, cylinders.

Section: Formulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A viable model for power focusing in a lossy cylinder

IEEE Trans. Antennas Propagat.

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2000

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“…A related area of investigation is in geophysical sub-surface probing where the aim has been to interrogate selected regions to ascertain their commercial value such as metallic ores and hydrocarbon deposits [4,5]. We have already analyzed a number of such problems using homogeneous but lossy half-space models where the excitation was from apertures with various illuminations [6,7]. We had also called attention to the similarity of such studies to near-field scanning of large antenna arrays [8].…”

Section: Introductionmentioning

confidence: 99%

Focusing of Electromagnetic Waves through a Conducting Sheet into a Lossy Dielectric Half-Space

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Journal of Electromagnetic Waves and Applications

1993

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The ability to focus electromagnetic fields into a lossy dielectric region is considered for the case where a thin highly conducting sheet is located between the source aperture and the observer. An exact formulation is presented for the aperture illumination which may be any function of the horizontal (x, y) coordinates. The resulting expressions for the fields in the homogeneous dielectric region, above or below the thin conductive sheet, are evaluated numerically for selected cases. In particular, it is shown that the presence of the sheet does not impair the quality of the focus to any major extent, but the amplitude of the field is diminished significantly. The double numerical integration routines are validated by developing relatively simple asymptotic expressions for the fields which also can be employed as dependable field predictors for regions not near the array.

Localizing the spatial and temporal electromagnetic fields on the axis of a lossy cylinder

IEEE Trans. Biomed. Eng.

Wait²

1994

Given a specified form, both in time and space, for the electromagnetic fields on the axis of a lossy cylinder, we determine, analytically, the required azimuthally symmetric source distribution on the surface of the cylinder that generates such internal fields. We then show that this source is equivalent to an array with finite number of cylindrical slots in a metal encasing that are impulsed by specified voltages at a finite sequence of discrete times. A confirming forward calculation exhibits excellent agreement between the specified field form and that generated by the array of cylindrical slots. Potential applications are to hyperthermic cancer therapy, bioelectromagnetics and nondestructive testing.