Deep-Implanted MIMO Antenna Sensor for Implantable Medical Devices

Abstract

A compact multiple-input–multiple-output (MIMO) implantable antenna is proposed in this article for deep-implanted medical devices. The suggested antenna enables high-data-rate telemetry as well as sensing the inner conditions of the tissues. It consists of two semicirc- ular patches that are excited with coaxial cables. The miniaturization in the suggested design is achieved using multiple slots in the patches, shorting pins, and high-permittivity substrate. Consequently, the antenna maintains a compact 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">$\pi \,\,\times6\,\,^{\mathrm{ 2}}\,\,\times0.13$ </tex-math></inline-formula> mm 3. Both elements of the antenna resonate at 0.915 GHz, possess a peak realized gain of −23.23 dBi, and maintain a low mutual coupling of −21.77 dB at 0.915 GHz. The effectiveness of the suggested antenna is verified using the specific absorption rate (SAR) and link budget analysis. Moreover, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${2} \times {2}$ </tex-math></inline-formula> MIMO channel parameters such as the envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity (CC) are calculated. In fact, CC using the suggested antenna reaches to 9.6 bps/Hz at a fixed SNR of 20 dB, which is almost two times more than that of the single-input–single-output (SISO) antenna (CC = 5.89 bps/Hz at SNR = 20 dB). The sensing ability of this antenna is demonstrated in addition to high-data-rate performance. The simulated and measured results confirm that it has almost similar radiation performance, impedance matching, and bandwidths for all dielectric properties of human tissues. Therefore, the proposed antenna is suitable for high-data-rate communication and monitoring pathological changes in deep tissues.