Investigation of a single‐plate π‐shaped multiple‐input–multiple‐output antenna with enhanced port isolation for 5 GHz band applications

A simple single‐plate, π‐shaped multiple–input multiple‐output (MIMO) antenna with built‐in port isolation operated at 5 GHz (5150–5850 MHz) band is proposed. The MIMO antenna is a symmetrical structure formed on a single‐layered FR4 substrate. The main radiating element is of a single‐plate π‐shaped structure, and is 4 mm away from the antenna ground. The ground plane in this design provides sufficient finite size to properly excite the antenna. The π‐shaped structure has a few desired features: a space saver, due to co‐location of impedance matching network and isolation structure; built‐in isolation and stable MIMO operations; existence of stationary current sink and source (S‐S/S) points, which were proven to be the key to enhance port isolation. Since the commonly referred neutralisation line (NL) technique does not exhibit S‐S/S points; thus, our design is not considered as a NL. The radiation patterns of the two planar inverted F antenna ‐like monopoles cover the complementary space regions of 45°–50°, the antenna yields peak gain varied from 2 to 3 dBi, and radiation efficiency was >60% at 5 GHz band. The antenna port envelope correlation coefficient was about 0.05.