Abstract
A compact, dual polarized, multiband four-port flexible Multiple Input Multiple Output (MIMO) antennae with the connected ground and high isolation is designed with computation and experimental measurement studies. All four monopole radiators are embedded decagon-shaped flexible FR-4 substrate with an outer radius of 10 mm in order to accomplish circularly polarized (CP) radiations, bandwidth enhancement, and compact size of only 45 x 38 x 0.2$ mm(3) (0.375 lambda x 0.316 lambda x 0.0016 lambda , at lowest resonating frequency 2.5GHz). The interconnected ground structure is loaded with an Interlaced Lozenge Structure (ILS) to suppress the surface wave radiations resulting in low mutual coupling between the radiators. The proposed MIMO antenna demonstrates measured 10-dB impedance bandwidths of 9.63% (2.37-2.61 GHz), 28.79% (3.30-4.41 GHz), and 16.91% (4.98-5.90 GHz) in the LTE 38/40, Sub-6 GHz 5G NR n77/n78, WLAN and Wi-Fi bands, respectively. Furthermore, broad 3-dB Axial Ratio Bandwidth (ARBW) of 28.79% (3.30-4.41 GHz) with gain greater than 4 dBi and efficiency above 80% are achieved. Finally, the bending analysis of the proposed flexible MIMO antenna along the X- and Y- directions shows good performances in terms of scattering parameters, 3 dB ARBW, and MIMO diversity parameters.