Wireless transfer of low power for low voltage implanted biomedical devices

Abstract

This dissertation studies the wireless transfer of power to implanted biomedical devices. Three different primary transmit coil geometries are investigated, namely spiral, solenoid and a Figure-8 geometry. Mathematical modeling and Finite Element Method (FEM) simulation were used in the analysis. Three dimensional mathematical models were developed and compared with commonly used, simplified two dimensional models. The coil characteristics are compared against each other for benchmarking purposes. It is found that the three dimensional models are more accurate at distances close to the coils. Circuit level parameters for the coils are extracted from the FEM simulation and compared to the theoretically calculated values of resistance and inductance. Finally, the coils are placed in the context of an inductive link circuit by employing secondary series and secondary parallel resonant topologies. The results show that the secondary series topology although more stable, is much less efficient with a 0.35% voltage transfer, in comparison to the parallel resonant topology which gave 13.5% voltage transfer.