Fields of a cell phone with a hands-free kit adapter

This paper examines the electric field inside a simple model of the human head, due to a cellular telephone with a “hands-free kit” (HFK) adapter. The cell phone is a metal box with a quarter-wave monopole on the top. The HFK wire is connected to the bottom of the handset and runs up parallel to the body to a point near the location of the ear. The body, neck and head are represented with box models, including layers for the skin, muscle, and bone in the head, which is filled with brain material. The fields due to the handset, monopole, HFK wire and head, neck and torso are found with the finite-difference time-domain method. The fields in the head due to the handset alone are the reference case. When the handset and HFK are operated in free space the fields in the region where the head would be are found to be stronger than those of the handset alone. When the body is present, the fields near the surface of the head with the HFK depend strongly on the spacing of the HFK wire to the body. However, for the two cases examined, the field strength in the brain with the HFK wire is always smaller than the field strength of the handset alone.