This paper presents a magnetic resonance wireless power transfer (WPT) system that uses three coils, a planar receiver and operates at 6.78 MHz,. Effective power transfer is ensured by establishing an impedance matching condition for this WPT system. A metamaterial (MTM) array having dimensions of 20 cm. 30 cm is also positioned near the load coil to concentrate the magnetic field and enhance the transfer efficiency. The result is a maximal improvement of 27% in the transfer efficiency at a transfer distance of 50 cm. The impact of a ground plane on the transfer efficiency is also examined. By utilizing the MTM array, making slits on the ground plane and increasing the gap between the ground plane and the load coil, it is possible to mitigate this impact. The highest transfer efficiency improvement is about 55% at a distance of 20 cm with the ground plane. A practical laptop model is fabricated to verify the impact of the load coil angle and position on the transfer efficiency. The result shows that the maximum transfer efficiency with the laptop model is 47.58% with the load coil angle of 90 degree(1)

This study presents the design and analysis of a magnetic resonant coupling wireless power transfer (MR‐WPT) system that employs planar textile resonators. To reduce the size of the system for wearable applications, the transmitter and receiver are designed and fabricated on a flat plane of fabric. A proposed symmetric four‐resonator MR‐WPT system is used for verifying the electromagnetic property of the textile substrates. Two textile substrates: polyester and cotton fibre are investigated to determine their impact on the transfer efficiency. Experiments show that the transfer efficiency is considerably higher with the polyester substrate than with the cotton substrate. In addition, copper tape and silver paste are employed for the resonator fabrication because of their flexibility. The measured results show that the copper tape has a significantly higher transfer efficiency than the silver paste because of its high conductivity. At a transfer distance of 5 cm, the maximum transfer efficiency is 50% with the polyester substrate and the copper tape resonator. Furthermore, the width of the coil‐pattern is varied to determine its impact on the resonant frequency and the transfer efficiency of the MR‐WPT system. This research confirms the feasibility of using flexible MR‐WPT for wearable applications.

The objective of this paper is to design a radiation pattern reconfigurable antenna that operates at the Medical Device Radio communications Service band (MedRadio band: 401-406 MHz) for medical implants. By spiraling a monopole, an antenna miniaturization is accomplished. Two artificial switches are employed to perform a radiation-pattern reconfigurable property. The proposed antenna has dimensions of 28 mm x 11.5 mm x 0.6 mm (193.2 mm 3 ) and utilizes substrate FR4 (ε r = 4.4). A one-layer skin model (ε r = 46.74, σ = 0.69 S/m) is adopted for the antenna simulation and in vitro test. Index Terms-Implantable antenna, Pattern reconfigurable, Medical Device Radio communications Service (MedRadio) band.

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This paper proposes a new method to increase the transfer efficiency of a wireless power transfer (WPT) system, having a source coil, a sprial transmitter (Tx) coil, a load coil and a ground plane, by utilizing the ground plane itself. The creation of cross slits at the ground center and employment of a lumped capacitor on the ground plane transform the ground plane into an additional resonator, which makes the original WPT system work as a 4‐coil WPT system, producing a higher efficiency. By experiment, with an optimized capacitor on the ground plane of C = 2180 pF, the measurement of transfer efficiency shows a maximum improvement of 10% at a transfer distance of 40 cm, compared to the case without the ground plane. The transfer efficiency of the proposed system at transfer distance of 15 cm is 46%. Circuit theory and electromagnetic simulations are employed to analyze the proposed WPT system, giving results consistent with the measured ones. The operating frequency of the proposed system is 6.78 MHz. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:514–521, 2017