Effects of dielectric values of human body on specific absorption rate (SAR) following 800 MHz radio frequency exposure to ingestible wireless device

Abstract

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 increased 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 original and changed 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 800 MHz. Results show that variation of radiation intensity near the surface of abdomen is around 1.6 dB within 20% variation of dielectric values at the frequency of 800 MHz. Electric fields in the anterior of the human body models are higher than those in the posterior for all scenarios. SAR values increase as the conductivities of human body tissues increase and usually decrease as the increase of relative permittivities of human body tissues increase. The effect of the dielectric values of human body on SAR is orientation, human body and frequency dependent. An increment up to 20% in conductivities and relative permittivities alone or simultaneously always causes a SAR variation less than 20%. As far as the compliance of safety was concerned, the IWD was safe to be used at the input power less than 9.3 mW according to IEEE safety standards.