Split ring resonator antenna system with cortical implant and head-worn parts for effective far field implant communications

We propose a spatially distributed antenna system to serve as the radio platform for RFID inspired brain care applications. The antenna system consists of a passive wearable part placed on the scalp and a cortical implant part with split ring resonator topology for miniaturization and antenna self-matching with a backscattering microsystem. We have optimized the antenna system in a hybrid head model combining anatomical features with a layered ellipsoid mimicking the major tissue layers of the human head in a controlled manner. Results from the wireless testing of the prototyped antenna system indicate that it enables remote powering and readout of a -18 dBm RFID microsystem at a distance of one meter at 915 MHz with 10 mm implant depth. Moreover, our experiment shows that the studied system is tolerant toward misalignment between the implantable and wearable parts.