Polarization Controlled Dual-Polarized MIMO Antenna With Enhanced Isolation for Full-Duplex WBANs

A polarization controlled dual-polarized multiple-input multiple-output (MIMO) antenna with enhanced isolation for full-duplex wireless body area network (WBAN) in the 5.8 GHz industrial, scientific, and medical (ISM) band is proposed. The advanced polarization control of each antenna element comprising the MIMO antenna is realized by embedding tailored T-shaped strips within the transversal slots of a main diagonal cut in the ground plane, which effectively steer the surface currents to a favorable direction to achieve the desired polarization with enhanced isolation. By slotting the twin circular patch radiating elements and incorporating twin capacitively coupled stepped elements adjacent to their feeding terminals, the proposed low-profile design realizes good impedance matching, return loss, and bandwidth. Experimental results demonstrate isolation greater than 5 dB compared with existing designs, and we report inter-port isolation that exceeds 33 dB for the 150 MHz bandwidth, with a peak isolation of approximately 67 dB. As a result, the proposed antenna exhibits low envelope correlation coefficient (ECC), high diversity gain (DG), and acceptable total active reflection coefficient (TARC) and channel capacity loss (CCL). A prototype antenna was tested under structural deformation by bending it along a -45∘ direction, with a simulated specific absorption rate (SAR) of 0.258 W/kg on a human phantom, thereby validating the antenna’s compliance with safety standards. The findings of this study demonstrate that the proposed design effectively addresses critical challenges in full-duplex WBAN antennas by enhancing port isolation, minimizing mutual coupling, and advancing polarization control, while maintaining a low-profile and low-complexity feeding network structure.