Scattering and absorption characteristics of lossy dielectric objects exposed to the near fields of aperture sources

The extended boundary condition method (EBCM) is used to obtain the absorption and scattering characteristics of lossy dielectric prolate spheroidal models of biological objects exposed to the near fields of large aperture sources. Two equivalent methods are employed to expand the incident fields, from the aperture sources, in terms of the vector spherical harmonics about the spheroidal origin. The results obtained for a spheroid located a large distance away from the aperture source agree well with those obtained from the corresponding plane-wave irradiation studies. Other near-field absorption characteristics are examined, and the applicability conditions for each of the two methods for obtaining the incident field expansions are discussed. In particular, it is emphasized that meaningful evaluation of hazardous levels of electromagnetic radiation should be made in terms of the magnitudes and the directions of the electric- and magnetic-field components, rather than the incident power density level. The calculated results also conform to the understanding previously obtained from studying irradiation of the spheroidal models of biological interest by plane waves and by near fields of various elementary radiation sources.