Electrode Design Theory Using Highly Accurate Equivalent Circuits in Biological Capacitive WPT

This letter presents an electrode design theory for capacitive biological wireless power transmission (WPT) using highly accurate equivalent circuits. First, we construct a lumped constant circuit that considers the permittivity and conductivity of the biological tissue and parasitic elements of the electrodes. Next, the sizes of the optimal electrodes that can achieve high efficiency within an area of
$30 \times 30\,\,\text {mm}^{2}$
are determined based on the relationship between electrode size and equivalent circuit elements. The experimental results show that the equivalent circuit and simulation can be accurately modeled. Furthermore, the horizontal misalignment is simulated to evaluate and prove the design’s resistance to misalignment. Finally, as a safety evaluation, the power that satisfies the specific absorption rate (SAR) requirements specified in IEEE-C95.1 is obtained, and it is determined that 71 mW of power can be received.