Flexible Tri-Band Dual-Polarized MIMO Belt Strap Antenna Toward Wearable Applications in Intelligent Internet of Medical Things

This article proposes a novel concept of flexible dual-polarized multiple-input multiple-output (MIMO) belt strap antenna with triple band. It can be integrated into the wearable biomedical network base station (WBNBS) of intelligent Internet of Medical Things (IoMT), setting up a communication link with smart mobile devices, thereby hosting wireless wearable sensors to track the vital signs of the human body. The proposed antenna includes three identical antenna units equidistantly distributed on the belt strap. Each unit is composed of two linearly polarized dipoles placed orthogonally. The goat horn-shaped outer loop and M-shaped inner loop produce the first and second bands, respectively, and their second harmonic jointly forms the third band. The arc-shaped coupled ring is connected with one dipole arm, which is conducive to tune impedance matching. The effects of belt strap bending and antenna radiation on the body are analyzed. Specific absorption rate (SAR) values are reduced by attaching the absorbing-shielding layer. As a proof of concept, the proposed antenna is fabricated for verification. Both measured and simulated results demonstrate the excellent performance with a realized gain of 2.2-3.1 dBi and radiation efficiency of 46.1%-80.1% in -10 dB impedance bandwidths of 2.37-2.7, 2.8-3.22, and 5.41-6.03 GHz. Finally, a smart belt prototype system is manufactured and tested. A link between wearable sensors and smartphones/computers is set up via WBNBS, where vital signs could be digitally displayed and monitored. It could provide a health risk alarm for a serious pandemic.