Metamaterial-enhanced MIMO antenna array system for non-invasive cerebral hemorrhage assessment in elderly and...

Microwave imaging (MWI) presents a promising, safer, more affordable, and portable alternative for detecting strokes compared to traditional methods, such as CT and MRI, which have limitations related to radiation exposure, cost, and accessibility. This paper focuses on the design and performance evaluation of a compact, T-shaped, two-port Multiple-Input Multiple-Output (MIMO) antenna, developed explicitly for microwave-based brain imaging. MWI operates by exploiting differences in tissue dielectric properties to identify and visualize abnormalities, with ultra-wideband (UWB) antennas configured in a two-port setup to improve signal penetration. The antenna, fabricated on an FR4 substrate with a dielectric constant (ε_r) of 4.3, effectively functions within the 3.1-6 GHz frequency range. It demonstrates a broad impedance bandwidth and maintains excellent isolation. Both simulated and measurement results confirm its reliable performance, showing consistent return-loss characteristics and stable omnidirectional radiation patterns. Furthermore, the antenna exhibits a very low envelope correlation coefficient (ECC < 0.005), a high diversity gain (DG > 9.9 dB), and favorable mean effective gain and total active reflection coefficient (TARC) values. When integrated into a human head model, this MIMO antenna configuration has shown minimal mutual-coupling (below - 15 dB) and significant potential for non-invasively detecting hemorrhages by carefully monitoring changes in scattering parameters. This proposed system underscores the capability of compact MIMO antennas to enable portable, non-invasive, and rapid stroke diagnosis, offering particular advantages for patients who lack access to conventional imaging facilities.