Miniaturised and radiation efficient implantable antenna using reactive impedance surface for biotelemetry

Abstract

This study presents the realisation of reactive impedance surface (RIS) in an implantable environment to design a compact wideband antenna for biotelemetry communication. The antenna is designed to operate at 2.45 GHz industrial, scientific and medical (ISM) band using a one-layer skin model. The proposed mushroom-based circular RIS successively improves the impedance matching, gain, and bandwidth of the antenna. The improvement in -10 dB impedance bandwidth and gain is observed by 270 MHz and 7 dB, respectively. The overall volume of the antenna is compact and measured only 99.69 mm3. The peak specific absorption rate value of the loaded antenna is noted at 595 W/kg for input power of 1 W, while the radiation efficiency of the antenna is noted by 7.5% at the resonance. The fabricated prototype is inserted into the minced pork and dipped into a skin mimicking gel for the measurement purpose. Furthermore, the link margin has been analysed, which predicts a possible transmission range up to 40 m for a signal bit rate ≤5 Mbps. The impact of associated circuit components on the antenna performance has also been investigated.