Scalp-Implantable MIMO Antenna for High-Data-Rate Head Implants

Abstract

A quad-element multiple-input–multiple-output (MIMO) antenna is designed at 433 MHz industrial, scientific, and medical (ISM) band, to increase the transmission data-rate and minimize the multipath fading. The proposed MIMO antenna consists of semicircular meandered radiators with a shared ground. It is designed and optimized inside an implantable medical device in a human head model. The antenna’s results show a 10 dB fractional bandwidth of 38.26% (355–523 MHz) with a peak realized gain of −28.3 dBi. A high isolation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 32.6 dB) between MIMO elements is obtained using a central metallic via. Specific absorption rate and link budget are analyzed to validate the effectiveness of this antenna. The 4 × 4 MIMO channel parameters are calculated and validated. Furthermore, this antenna provides a channel capacity of 19.9 bps/Hz which is about three times higher than the single-input–single-output configuration of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx$</tex-math></inline-formula> 5.89 bps/Hz. Hence, this MIMO configuration is a promising candidate for high-data-rate head implants.