Figure 1: Simulations were performed to estimate mid-field coupling efficiency and specific absorption rate (SAR) of radiation.

(A) The multilayer tissue model (not drawn to scale) used in simulation studies consists of 2 mm of skin, 20 mm of fat, 10 mm of muscle, and 18 mm of stomach tissue arranged as shown. Antennas are placed 4 mm away on either side of the tissue model. (B) The simulated transmission coefficient or S₂₁ parameter is shown as a function of distance through the multilayer tissue model. The dotted lines show the transitions between different tissue. From left to right, they are: air-skin, skin-fat, fat-muscle, and muscle-stomach tissue. The efficiency across the complete multilayer tissue is about −41 dB. (C) For the SAR calculations, a 10-g mass of tissue (striped blue; a cube of tissue of side length 2.15 cm, not drawn to scale), directly under the center of transmitting antenna, was used. The location of the tissue was based on inspection of the SAR in different planes in the x-axis, as indicated by the labels on the right side of the tissue model. (D) The relative magnitude of SAR is shown in different slices (planes in the x-direction). Each slice is labeled with its distance from the transmitting antenna. Red indicates regions of high absorption, while blue indicates regions of low absorption. In the slices that are outside of the tissue (at x = 1 and x = 58 mm), the magnitude of the mean-squared electric field is plotted instead of the absorption. The color scale is for qualitative comparison within a slice only, as the scale differs among slices. (E) Averaged value of SAR is as a function of the power delivered into the transmitting antenna. IEEE sets a low-tier (blue) and high-tier (red) standard for safety limits.