Specific absorption rate and temperature increase for a passive brain implantable medical device using transmission line analysis

The power transfer to implantable medical devices (IMDs) has recently gained notable attention to avoid battery-assisted implantable devices. External power is provided to battery-less IMDs through near-field inductive/capacitive coupling, mid-field electromagnetic (EM) coupling or far-file EM coupling. The potential adverse health effects produced by electromagnetic exposure have to be considered to ensure safety. Owing to the fact that planar wave electric field is equivalent to the voltage in lossy transmission lines, circuit simulation can be used to approximate absorption of EM fields in the biological tissues. In this paper, we calculate the specific absorption rate (SAR) and temperature rise due to EM fields exposure using circuit simulation at medical device radio communications (MICS) band (402 MHz). The lossy transmission lines parameters are obtained from the 4
^th
-order Cole-Cole model at 402 MHz. The obtained results from the circuit simulation are compared with full-wave simulation, yielding a maximum difference of 31% in SAR at the skin layer and negligible difference in the temperature rise due to EM fields exposure.