A Compact FSS-Based Four-Port MIMO Antenna for Low Mutual Coupling

This letter presents a four-port multiple-input–multiple-output (MIMO) antenna based on frequency selective surface (FSS) for X-band communication. The suggested MIMO antenna is composed of four-slotted circular microstrip patch elements, which have been planned on an FR-4 substrate with a low profile (0.91λ
₀
× 0.91λ
₀
× 0.045λ
₀
). The suggested antenna reduces mutual coupling (MC) and enhances gain based on the FSS technique. The band-stop FSS transmission coefficient is below −10 dB over the 7.2 to 9.1 GHz range. Additionally, for transverse magnetic and transverse electric polarization, the planned FSS offers a steady frequency response for incidence angles up to 40°. The suggested MIMO antenna bandwidth is from 7.8 to 9.08 GHz (15.4%), with a peak gain of 5.2 dBi. The MC < −20 dB is attained over the entire operating bandwidth. In addition, the suggested antenna envelope correlation coefficient is <0.005, diversity gain is <9.99, and channel capacity loss <0.3 bps/Hz is obtained in the operating frequencies band, approving good MIMO diversity performance.