A defected substrate 4-element mimo antenna with higher diversity characteristics for 5G sub 6 GHz N77/N78 band applications

A unique miniatured 4-port MIMO (multiple input multiple output) antenna employing defected substrate having footprint of 58 × 58 × 1.6 mm³ has been developed for 5G sub-6 GHz N77/N78 bands. The antenna is made on FR4 substrate (relative permittivity = 4.4, height = 1.6, and loss tangent = 0.02). The design comprises four circular slotted octagonal-shaped radiators on top and defected ground with ground patches on the bottom of the substrate. Every octagonal radiator is loaded with a circular slot to enhance impedance-matching. The ground comprises rectangular partial ground and an octagonal-shaped ground patch beneath each radiator. The isolation among adjacent radiators is improved by orthogonal radiators and defected substrate. The antenna is developed, and the simulated results are verified. The antenna resonates at 3.5 GHz covering 5G sub-6 GHz N77/N78 band. Aside from measured bandwidth of 1.1 GHz (3.1–42 GHz) having isolation > 15 dB, the antenna also displayed adequate gain of 3-4dBi and radiation efficiency of 90%. Moreover, the MIMO characteristics like envelope correlation coefficient < 0.00001, diversity gain of 10 dB, channel capacity loss of < 0.02 bps/Hz, total active refraction coefficient of < − 10 dB, mean effective gain < − 3 dB and omnidirectional features are achieved. Because the modelled and observed results correlate so well, the antenna is a promising candidate for 5G sub-6 GHz applications.