Coupled Resonance Energy Transfer Over Gigahertz Frequency Range Using Ceramic Filled Cavity for Medical Implanted Sensors

Abstract

A wireless power transmission (WPT) system based on a magnetically coupled coil-based resonance is the predominating technology in most WPT applications. In the field of implantable medical devices, however, the energy transfer operation is highly limited by the size of the receiver and also the loss properties of dispersive human tissue. Since the low gigahertz range has been considered as the optimal transfer frequency, an alternative to the lossy coil resonator should be studied and developed. In this paper, an original transmitter solution is presented that considers the needs for strong magnetic dominant near-field and weak far-field radiation even at low gigahertz frequency. A half-closed partially ceramic-filled cavity resonator is described on the basis of an accurate, but analytical model. Design parameters are also studied using a full-wave simulation software package and measurement results of a resonator-to-resonator transfer scheme are presented, which show a good agreement with simulation results. An efficiency above 65% can be obtained within the distance comparable to the diameter of the resonator (60.5 mm) in this case study. Subsequently, energy transmission between the proposed cavity resonator and a small-sized copper coil of 3 mm of diameter is investigated. Measurement results show that the efficiency is above 34% within 20 mm and above 8.2% within 40 mm, which is much higher than the conventional coil-to-coil transmission scheme.