Microstrip-Ministered Proximity-Coupled Stacked Dual-Port Antenna for 6G Applications

A novel dual-port multiple-input-multiple-output (MIMO) antenna arrangement is introduced for attaining quasi-omnidirectional circular polarization (OCP) towards device-to-device (D2D) integrated sensing and communications (ISAC) deployment in sixth generation (6G) networks. The antenna architecture comprises of three dielectric laminates arranged one below/above the other with each substrate juxtaposed to its counterpart by the air cavity. The upper laminate encompasses solitary element frequency selective surface (FSS) etched on both fronts. Impedance matching transmission lines and partly reactive impedance surfaces (RIS) were printed on the top and bottom region of the middle substrate, respectively. The lower laminate features microstrip feed lines on the top side and semi ground planes on the bottom. The MIMO antenna was made up of two ports and fed through proximity coupling from the opposite ends of the middle substrate’s top surface to resonate with a −10 dB impedance bandwidth (I-BW) of $\sim $ 35%. The partial RIS enabled $>$ 20 dB of isolation between the ports while the air cavities between the laminates contributed to achieve a realized gain of $>$ 7 dBi. The antenna occupies $1.2\lambda \times 1.2\lambda $ footprint and $0.1\lambda $ height at 12 GHz to exhibit quasi-OCP in the azimuth plane with axial ratio (AR) of < 3 dB and efficiency of $>$ 90%. The envelope correlation coefficient (ECC), diversity gain, specific absorption rate (SAR), and power density (PD) at the band of interest were < 0.1, $\sim $ 10 dB, < 1.6 W/kg, and < 10 W/ $\text{m}^{2}$ , respectively. The results of the Ansys HFSS simulations and the measurements taken within the anechoic chamber exhibited good agreement. In contrast to state-of-the-art quasi-OCP antennas operating in the 12 GHz spectrum, the novelty of the proposed MIMO antenna includes a straightforward and compact configuration that is integrated synergistically to provide reasonably high gain and efficiency values.