Wideband Low-Profile Eight-Port Eight-Wave Annular-Ring Patch Antenna Based on Using Eight Dual-Shorted Dual-Resonant Ring Sectors for 8 × 8 MIMO Mobile Devices

A wideband eight-port eight-wave annular-ring (AR) patch antenna for
$8\times $
8 MIMO mobile devices is presented. The AR patch antenna is formed into eight dual-resonant 45o-ring sectors to radiate eight very-low-correlated or generally uncorrelated waves for
$8\times $
8 MIMO application. Each ring sector is loaded with two shorting pins and excited by a simple probe feed to generate its half- and quarter-wavelength resonant modes at close frequencies to form a dual-resonant wide operating band. Additionally, all 16 shorting pins of the eight ring sectors have a same distance to the patch center, thereby forming a shorting circle to function like a circular metal wall in the AR patch. This makes the surface currents coupled from the excited ring sector to adjacent sectors to be mainly confined inside the shorting circle. Therefore, with the eight probe feeds located outside the shorting circle in the AR patch, enhanced port isolation is obtained. With the proposed design, the eight-port AR patch antenna having a low profile of 1.4 mm (about
$0.028\lambda $
at 5.9 GHz) and an outer diameter of 46 mm (about
$0.91\lambda $
at 5.9 GHz) can generate eight very-low-correlated waves over a wide band of about 5.9-7.2 GHz (fractional bandwidth 20% based on 3:1 VSWR for mobile device application). Also, the proposed antenna has a back ground plane and is especially suitable for on-metal surface application. The use of a single proposed antenna can be conveniently applied for the mobile device or Internet-of-Things (IoT) device to cover such as 5.925-7.125 GHz for
$8\times $
8 MIMO operation in the possible new mobile communication spectrum.