Design of a Miniaturized Omni-Directional RF-to-dc IR-WPT

This paper proposes the design and experimental validations of a 13,56 MHz IR-WPT link with a conformal transmitter (Tx) and a miniaturized (about 1 cubic centimeter) receiver (Rx). The Rx is composed of three receiving coils wrapped around a miniaturized sphere and mutually orthogonal, arranged in such a way that quasi-constant dc-output voltage and efficiency are obtained, regardless of the receiver orientation in 3-D. The conformal transmitter is designed to maximize the coupling coefficient, at a reference distance of 5 cm, and is about 7 × 10−3. The quasi-constant output voltage is obtained by connecting each Rx coil to its class-E rectifiers, optimized together with the rest of the system, and by series-connecting their dc output ports, thus de-facto removing any possible dark zone. With a 10-V input source, the dc-output voltage is always above 2.7 V and an average conversion efficiency of 13% for any possible 3-D receiver orientation is obtained.