Desenvolvimento de novos ressoadores para transmissão de energia sem fio aplicados em Dispositivos Médicos Implantáveis

Abstract

This work presents the analysis and design of new configurations of microwave planar resonators with the proposal of integrating systems for wireless power supply of implanted medical devices. Over the last few years, implantable medical devices (IMD) have become protagonists in assisting diagnostic, prognostic and medical treatment tasks. Most IMD require a form of power supply to operate, which is often done through the use of batteries, thus demanding periodic maintenance and invasive surgical procedures. The wireless power transfer (WPT) technology employed in this scenario presents itself as a promising alternative solution. This thesis is situated in the context of proposing new models of compatible resonators that can be integrated into WPT solutions for IMD power supply. In this work, two WPT techniques were explored: inductive coupling (non-radiative/near field) and planar antennas (radiative). The analysis and design were carried out through the analytical and parametric study of the proposed models using computational electromagnetic simulation tools. A series of technical parameters were verified, with emphasis on the operating frequency, physical dimensions, efficiency, positioning sensitivity, and safety parameters, such as the specific absorption rate (SAR) and admissible power range. Using low-loss dielectric substrates (RO3006 and RO3010), three prototypes were built, designed for operation in the 0,403, 0.915 and 2.45 GHz frequencies, which are part of the MedRadio and ISM bands. Via inductive coupling, it was possible to obtain a system with transfer efficiency greater than 50% at a separation of 8.0 mm of tissue, enabling an admissible power of up to 120 mW for a safety limit of 2.0 W/kg of SAR. Using a planar antenna, a model with dual operating band (0.9 and 2.45 GHz) and circular polarization was obtained, achieving efficiency levels of 0.57 and 1.12% with reduced physical dimensions. The experimentally measured results demonstrated good agreement with the computational analyses and led to promising conclusions regarding the performance of the proposed resonators.