Four-Port Wideband Annular-Ring Patch Antenna Generating Four Decoupled Waves for 5G Multi-Input–Multi-Output Access Points

A four-Port annular-ring (AR) patch antenna generating four decoupled waves in 3.3–5.0 GHz (41% at 4.15 GHz) with antenna efficiency better than about 84% and envelope correlation coefficients (ECCs) less than 0.05 is presented for fifth-generation multi-input–multi-output (MIMO) access-point applications. The AR patch is placed 10 mm above the ground plane and its four ports are equally spaced by 90° (at
$\varphi = 0^{\circ }$
, 90°, 180°, 270°) in the patch. Each Port is surrounded by a ring gap to achieve enhanced impedance matching. Additionally, four gap-coupled shorting (GCS) strips equally spaced by 90° (at
$\varphi = 45^{\circ }$
, 135°, 225°, 315°) are added to short-circuit the patch to the ground plane, so that two adjacent ports are separated by one GCS strip. The arrangement makes the four ports capable of generating four decoupled waves with very low ECCs in 3.3–5.0 GHz. An extended design to achieve better isolation between ports is also addressed.