Reconfigurable circular patch MIMO antenna for 5G (sub-6 GHz) and WLAN applications

In this article, a circular patch microstrip feed line monopole radiator with a dimension of 15 x 20 x 1.6 mm(3) is proposed. An inverted L-shaped stub is employed in the partial ground plane to achieve optimum bandwidth, radiation pattern and radiation efficiency. To further cover the sub-6 GHz spectrum (3.4-3.8 GHz) for future 5G communications, a two-element MIMO antenna configuration is designed by utilising the single element antenna. The edge-to-edge distance between the two elements is 0.15 lambda(0) (15 mm). The propose antenna achieved dual-operating bands of 3.35-4.60 and 4.93-5.19 GHz in the diode (D) = ON state. The minimum isolation between 3.35-3.94 and 4.99-5.16 GHz frequency range is -14.5 and -12.5 dB, respectively, by incorporating a rectangular stub between two inverted L-shaped stubs. The MIMO antenna has a peak gain of 2.68 dBi at 5.1 GHz frequency. The average total efficiency at port-1 between 3.35-3.94 and 4.93-5.19 GHz frequency range is 65%, whereas at port-2 is 75%. In terms of the envelop correlation coefficient (ECC), mean effective gain (MEG) and total active reflection coefficient (TARC), the proposed antenna's diversity performance characteristics are investigated and the obtained values are 0.09, +/- 3 and -3 dB, respectively. The suggested MIMO antenna is designed on a FR4 substrate with a dielectric constant of 4.4 and an electrical dimension of 0.34 lambda(0) x 0.20 lambda(0) x 0.015 lambda(0) mm(3) (where lambda(0) represents the free space wavelength at lower cut-off frequency [2.95 GHz]). Therefore, the proposed antenna can find applications for rain or fog as well as for identification and tracking (weather radar) on S-band at 3 GHz frequency, 5G (sub-6 GHz) and WLAN applications.