A Highly Efficient & Low-Mutual Coupling Partial Π/8 SIW Cavity Based 8-Port MIMO Antenna

 A sector-shaped compact π/8 partial substrate-integrated waveguide cavity antenna from the TM220 diagonal mode of the SIW cavity is presented. A 61% size miniaturization is achieved compared to the SIW rectangular cavity in its complete mode configuration. The compact cavity radiator is used as an element of a compact 8-port multiple-input multiple-output (MIMO) antenna. The 8-port MIMO antenna occupies the entire full cavity with slots loaded on the top and bottom layers. The fabricated prototype has a -10 dB impedance bandwidth (BW) from 6.006-6.143 GHz. The mutual coupling within the BW is less than -21 dB. The presented MIMO antenna has an envelope correlation coefficient (ECC) less than 0.0027, and a percentage diversity gain reduction below 1.73%, which makes it a suitable candidate for use in MIMO-based wireless communications (This paper has been accepted for publication in  IEEE Antennas and Wireless Propagation Letters )