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A semi-analytical method is presented for the assessment of the induced electromagnetic field inside a multilayer spherical head model exposed to radiation of an arbitrary source antenna. First, the isolated source antenna is simulated in a full-wave software to evaluate its radiation characteristics. By sampling the radiated fields, their spherical vector wave function (SVWF) amplitudes are evaluated. Next, the well-known translation addition theorem for SVWFs is implemented to translate the SVWFs of the radiated fields to the local coordinate system of the head model. It’s assumed that the presence of the head model does not affect the primary radiated fields by the antenna due to the adequate distance between them. By applying the boundary conditions on the head model, the unknown SVWF amplitudes of the induced fields inside each layer as well as those of the scattered field outside the model are evaluated. The verification of the proposed method is shown through some numerical examples. In comparison with a fullwave numerical method, the proposed method provides an efficient repeatable simulation approach due to the independent analysis of the source and head model, provided that the reaction of the head model to the antenna is negligible.
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