Electromagnetic modeling of spherical head using dyadic Green´s function

Antenna radiation pattern and other characteristics are significantly altered by the presence of the human head. When considering possible biological effects of electromagnetic (EM) fields, it is important to distinguish between field strengths outside the subject, and those within the body. The relationship of fields outside and within the body (called coupling) varies greatly with frequency. This paper aims to express an exact general representation of dyadic Green´s function (DGF) for the problem of electromagnetic radiation from a source of excitation in the presence of a human head model (multi-layered homogeneous lossy dielectric spherical model), which is valid everywhere, including the source region. The medium is assumed to be homogeneous, isotropic, linear, non-dispersive and stationary. The DGFs are obtained by employing the method of scattering superposition. Alternatively a compact general expression has been developed to determine the electric and magnetic type DGFs giving clarity as well as more efficient and economical computation in terms of speed, time and memory