Four ports wideband drop-shaped slot antenna for MIMO applications

In this paper, a proposal of a four-port antenna for MIMO applications is presented with high interport isolation. The isolation among elements is implemented by limiting the surface current distribution of each radiator by placing them on different substrate layers, leading to a size optimization. The array is implemented by four drop-shaped slot radiators. The antenna performs from 1.7 to 7.2 GHz, presents a very low Envelope Correlation Coefficient (ECC), reaching values of 0.0025 tops, and a stable Total Active Reflection Coefficient (TARC) over the entire operational bandwidth. These parameters demonstrate the feasibility of the antenna for MIMO systems. The peak average gain is 5 dB, and the port isolation between adjacent radiators, S ₁₂ and S ₁₄, and opposite radiators, S ₁₃ and S ₂₄ are below −20 dB, reaching values even less than −30 dB in some bands without adding extra structures, avoiding an increment in the total area.