Closely spaced MIMO antenna based on substrate‐integrated waveguide technology

In this letter, a compact array system for multiple‐input‐multiple‐output (MIMO) applications is designed, based on substrate integrated waveguide (SIW) technology. In order to verify the potential of the proposed antenna as a MIMO application, 2 types of 4‐element SIW antenna are placed in a compact space. Four isosceles triangle (type 1) and rectangle (type 2) SIW antennas, consisting of metallic vias at 1 side and slit at the other side, are used as radiating elements. The side‐to‐side distance of the elements is only 0.006 λ0. The peak gain of these patterns is −3 dBi. The envelope correlation coefficient is calculated from the measured 3D patterns and shows good MIMO performance. The proposed antenna achieves both a significant reduction of size and mutual coupling by metallic vias.