Effects of Dielectric Values of Human Body on Radiation Characteristics of Ingestible Wireless Device Following 1200 MHz

In order to assess the compliance of Ingested Wireless Device (IWD) within safety guidelines, the Specific Absorption Rate (SAR) and near fields of IWD in two realistic human body models whose dielectric values are changed from the original by ±±10 and ±±20% are studied using the Finite-Difference Time-Domain (FDTD) method. The radiation characteristics of the IWD in the human body models with changed and original dielectric values are compared. Simulations are carried out at 13 scenarios where the IWD is placed at center positions of abdomens in the two models at the operation frequency of 1200 MHz. Results show that variation of the radiation intensity near the surface of abdomen is around 3.5 dB within 20% variation of dielectric values. Electric fields in the anterior of the human body models are higher than those in the posterior for all scenarios. SAR values increase with the increase of conductivities of human body tissues and usually decrease with the increase of relative permittivities. The effect of the dielectric values of human body on SAR is orientation, human body and frequency dependent. A variation up to 20% in conductivities and relative permittivities alone or simultaneously always causes a SAR variation less than 30%. As far as the compliance of safety was concerned, the IWD was safe to be used at the input power lower than 8.4 mW according to IEEE safety standards.