A Compact Implantable MIMO Antenna for High-Data-Rate Biotelemetry Applications

Abstract

This article presents a low-profile multiple-input–multiple-output (MIMO) implantable antenna system, including a capsule endoscopy and a scalp implantation at medical implant communication service (MICS) band (402–405 MHz), and industrial, scientific, and medical (ISM) band (433.1–438.8 MHz). It consists of two elements with an edge-to-edge gap of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0018\lambda _{g}$ </tex-math></inline-formula> and overall dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi \times (5.65)^{2} \times 0.13$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and is placed on a 0.13 mm-thick RO3010 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\epsilon _{r} = 10.2$ </tex-math></inline-formula> and tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta = 0.0022$ </tex-math></inline-formula> ) substrate. The antenna is integrated with batteries, sensors, and electronic components in two different types of implantable devices (capsule and flat-type devices). The simulation result shows that the antenna has a fractional bandwidth (FBW) of 33.9%, a maximum realized gain of −30 dBi, and isolation of more than 26 dB. The fabricated prototype is measured in a saline solution and minced pork meat. The measured results are found in good accordance with simulations. The antenna parameters are calculated and showed a significant independence between the radiators. A link budget is estimated to be 78 Mb/s for a distance of 20 m. Thus, the proposed antenna is considered as a promising solution for high-data-rate medical applications such as capsule endoscopy, live surgeries, and other biomedical applications where the high data rate is required.