Evaluation of a Wireless Power Transfer System with Helmholtz and 3D coils for Biomedical Capsules

Wireless Power Transfer (WPT) systems are commonly found in battery charging solutions for electronic devices such as smartphones and tablets. In medicine, they are applied in biotelemetry systems with implantable units and in capsules to monitor parameters of the gastrointestinal tract. Several studies explored WPT systems with inductive links formed by two or more coils. However, few studies have considered inductive links with Helmholtz coils for application in capsules. This paper presents the development of a prototype of a WPT system suitable for monitoring capsules formed by live coils, three of which are a set of 3D receiver coils. The development of a class E amplifier allowed the power delivery to the link. In the experiments performed, the maximum energy (power) received in the load was 662.2 mW for the closest distance between transmitter and receiver coils, while the efficiency reached 3.31 %. Furthermore, the maximum achieved distance that maintained the regulated 3.3 Vcc power supply at load was 240 mm, even with changes in the orientation of the set of 3D receiver coils.