Resonant Inductive Power Transfer System for Freely Moving Capsule Endoscope with Highly Uniform Magnetic Field

Uniform magnetic field (H-field) is highly important for resonant inductive power delivery to a freely moving implantable biomedical device. Where the highly uniform H-field can minimize fluctuation of received power and at the same time lower down the unwanted peak electromagnetic exposure. In spite of that, the existing research has not fully addressed this issue. Thus, this paper presents a resonant wireless power transfer system which is configured with a new power transmission coil that produces highly uniform H-field. The coil is configured for optimum H-field uniformity, quality factor as well as power transfer efficiency. The optimum configured coil attained around 94% of H-field uniformity within 75% region inside the transmitting coil. This uniformity was around 46% higher than that attained by the typical Helmholtz coil, thus, the proposed coil tremendously minimized the fluctuation of the received power and the peak electromagnetic exposure. With a power receiving coil of empty set 11 mm x 8 mm, the power transfer system attained at least 10.5% of inductive link efficiency when at least 520 mW of power is transferred to a 30 Omega load.