Study of Nano-structure Coupling Micro-ScaleAntenna for Signal and Power Transmission using Magnetic Induction to an Implanted Device in the Human Body

Abstract

Currently, communication systems using radio frequency (RF) are the mainstream of functional devices. In the case of wireless communication devices such as mobile phones, tablet PCs, and medical devices, they can transmit an electrical signal from one device to another without a wire connection. However, this tech-nology is not suitable for the power transmission due to limitations such as low power efficiency and noise caused by interference from outside objects. Furthermore, the path loss is more severe when RF technology is applied to power transmission between an implanted human sensory system and external interfaces to transfer power, since 80 % of the human body is composed of water molecules. To overcome these limita-tions, this study focuses on magnetic induction (MI) system, which uses magnetic coupling of a pair of coils to transmit signals and power between devices. For magnetic fields, the path loss of water or other liquid media is smaller than that of RF waves. So far, most research results related with magnetic induction system have shown power transmission using macro-size coil structures. However, medical implant devices have the limit of the physical dimensions which requires the coil structure as small as possible. Unfortunately, a mi-cro-size antenna can have poor transmittance efficiency due to its size effect. Therefore, micro-size antennas with advanced structures should be investigated to overcome these challenges. This paper describes the coil designs and the characteristics of power transmission between a transmitter (Tx) and a receiver (Rx). To en-hance the magnetic inductance, a three dimensional magnetic core consisted of ZnO nano wires coated by a nickel (Ni) layer is added to the center of antenna structure. ZnO nano wires easily supply a large effective surface area with a vertical structural effect to the magnetic core structure, which induces a higher magnetic inductance with a ferro-magnetic material Ni. The magnetic induction coil with the magnetic core shows a high inductance value, a low reflection power and a strong power transmission. ⓒ 2014 DGIST