Four-Port Triple-Band Implantable MIMO Antenna for Reliable Data Telemetry in Wireless Capsule Endoscopy and Deep Tissue Applications

In this study, we propose a miniaturized triple-band multiple-input-multiple-output (MIMO) implantable antenna having four ports designed for the real-time transmission of high-quality images and videos for wireless capsule endoscopy (WCE) and deep tissue applications. The proposed antenna operates in the industrial, scientific, and medical (ISM) bands of 0.902–0.928 GHz for data telemetry and 2.400–2.4835 GHz for power-saving applications and midfield band (1.704–1.833 GHz) for seamless wireless power transfer (WPT). The antenna has a compact size of <inline-formula> <tex-math notation="LaTeX">$7.5\times 10.5\times 0.127$ </tex-math></inline-formula> mm3, achieved through the utilization of meandered resonators. The use of meandered resonators also resulted in reduced coupling between the MIMO elements due to opposite flowing current cancellation. The presented MIMO antenna, optimized inside a realistic capsule with batteries, sensors, and electronic components, was fabricated and tested. Simulated and measured results in terms of S-parameters and radiation patterns correlated well with measured bandwidths of 90, 129, and 200 MHz and measured gains of −37.3, −30.3, and −27.9 dBi at 0.915, 1.780, and 2.450 GHz, respectively. Verification of the specific absorption rate (SAR) affirms that the suggested antenna is suitable for utilization within the human body. In addition, based on the link-budget analysis, it can be confirmed that the presented implantable MIMO antenna can establish a reliable communication link up to distances of 14, 9, and 6 m at 0.915, 1.780, and 2.450 GHz, respectively, for transferring high data rate (78 Mb/s) information. Moreover, an assessment of MIMO and diversity performance, specifically with regard to envelope correlation coefficient (ECC) and diversity gain (DG), was conducted, revealing results that fell within acceptable limits. To the authors’ best understanding, this marks the first four-port triple-band implantable MIMO antenna specifically designed for applications in WCE and deep tissue scenarios.