SAR reduction and link optimization for mm-size remotely powered wireless implants using segmented loop antennas

This paper describes an approach to reduce the average specific absorption rate (SAR) of a wireless power link for mm-size cortical implants, while decreasing the loss of the overall link by using a segmented loop transmit antenna. It further shows that, for a given receive antenna size and antenna separation, an optimum transmit antenna size-frequency pair that minimizes the link loss exists. A case study of a wireless link for a mm-size cortical implant optimized for minimum loss shows a reduction of the average SAR of more than 30 %, and a link loss improvement of approximately 10 %, leading to a 57 % increase in power available to the implant compared to a conventional loop antenna.