ESTIMATION OF SPECIFIC ABSORPTION RATE USING INFRARED THERMOGRAPHY FOR THE BIOCOMPATIBILITY OF WEARABLE WIRELESS DEVICES

Wearable wireless technology has developed as an exciting topic over the last couple of years. With the extensive use of Wearable Wireless Devices (WWD) in greater proximity to the body for various wireless applications, the concern about biological effects due to the interaction of human tissues with the radiations is growing. In this research, we investigate the application of Infrared Thermography (IRT) to obtain temperature dynamics and reconstruct Specific Absorption Rate (SAR) to evaluate the exposure amenability of WWDs. A microstrip monopole antenna on a wearable substrate is used to determine the biological effects of the interaction of electromagnetic (EM) waves on the body. SAR is obtained using EM field simulations and by reconstruction from thermal measurements with the use of bio-heat equations for a continuous exposure of 300 s. Validation of IRT to reconstruct SAR is demonstrated by comparison with EM computations. The maximum SAR was 32mW/kg, for simulations and 35mW/kg, from reconstruction after IRT experiments. The maximum temperature change in both cases was always less than 1◦C. The difference between the SAR obtained through IRT and simulation tools accounted for an average of 8.7%. Information acquired using IR temperature dynamics can yield SAR values which can assess radio frequency exposure compliance for WWD at frequencies used for modern wireless technologies, with reliability.