Enhancement of Wireless Transmission Into the Human Body by Using Metasurface Matching Layer

This paper presents an innovative approach to minimize reflection losses at the air-tissue interface in biomedical applications. The utilization of a metasurface matching layer (MS-ML) is proposed to mitigate losses by modifying the wave impedance at the interface. Initially, a planar configuration of an implantable loop antenna is designed within a three-layer tissue model (skin, fat, and muscle) to be used as a receiving (Rx) element. To establish the wireless transmission link, a planar loop antenna is also designed in the air environment adjacent to the three-layer tissue model, serving as the transmitting (Tx) element. The system is designed to operate in the industrial, scientific, and medical (ISM) frequency band of 2.45 GHz. Furthermore, a rectangular MS structure with an optimized array combination of 2 × 2 unit cells is placed over the skin tissue to minimize reflection losses at the air-tissue interface. The design approach of the MS employs a transmission line model, focusing on retrieving the MS impedance and tuning it to compensate for the three-layer body impedance. Full-wave simulation studies showcase a notable enhancement in transmission strength of about 2.59 dB due to the use of the MS.