Comparison study on specific absorption rate of three implantable antennas designed for retinal prosthesi systems

The recent development in retinal prostheses brings the hope to restore the vision of blind people. Currently, research efforts have been largely focused on improving the electrode array of the system. However, the electromagnetic exposure to the surrounding area inside a human head caused by the implanted antenna system has been often overlooked. The authors investigate the specific absorption rate distributions inside a multilayer human head model for three implantable rectangle spiral microstrip antennas operating at different frequency bands as well as for one inductive coil antenna, which is popularly used for near-field data and power telemetry. The simulation results, which were obtained by using computer simulation technology Microwave Studio software, suggest that the Medical Implant Communication Service frequency band is the most suitable frequency choice for the currently proposed implanted retinal prosthesis systems. However, with the increase of stimulation electrode density, a higher frequency band might have to be chosen in the future to accommodate the increased bandwidth requirement.