Far-Field Backscattering Brain Implant Communications : Antenna Design Methodologies and Performance Validation

The recent progress in wireless technology has prompted the development of wireless implantable and wearable systems to realize the envisioned bio-telemetry where the patients can access to diagnosis and treatment at any time, any location and with any amount of monitoring and diagnostic data. Especially in brain care applications, wireless intracranial implantable microsystems are believed to open a new paradigm for the management of brain disorders and the treatment of neurological diseases. Planning the transcranial wireless link between the implant and the external devices is a challenging task that requires multidisciplinary considerations. The fundamental challenge is the attainment of miniature implantable antennas achieving adequately high efficiency for signaling and wireless power transfer in the presence of the dissipative intracranial tissues. Moreover, in the antenna development, accurate modeling of the human tissue environment is of great importance to characterize the antenna performance and to evaluate the tissue interaction with the electromagnetic radiation. Importantly, for the sake of the patient’s safety and comfort, extra-low power consumption with a batteryless operation of the implant is highly appealed to minimize the biological intrusiveness and to ensure a long-term operation. For this reason, radio frequency identification (RFID) technique, which is based on the extra low-power and low-complexity backscatter communications, has been recently considered as a promising wireless solution for the implants. To address the above-mentioned challenges, this thesis starts with a discussion of the RFID based wireless sensing, numerical modeling of the intracranial tissue environment and the characteristics of antenna radiation in lossy tissue materials. During this discussion, an approach to enable the semi-passive operation of an RFID system without the assistance of external batteries is presented, and a guideline for efficient modeling of the human head for implantable antenna development is provided. Finally, a multimodal spatially distributed antenna and a miniature dual- split-ring antenna with tuneable impedance are introduced for far-field backscattering brain implants. The promising performance of the proposed antennas is analyzed and discussed with simulation, in-vitro measurement and in-vivo experiment