Isolation-enhanced four-element MIMO antenna system using mushroom

In this paper, double-layer mushroom walls are vertically positioned in between a four-element substrate integrated waveguide (SIW) cavity-backed slot (CBS) MIMO antenna system for the inter-element isolation enhancement. A piece of mushroom wall comprises two printed circuit boards (PCB), two identical patches of mushroom cells are symmetrically printed onto both the surface of the PCBs, the shared ground is sand-wiched in between, and a vias connecting the patches to the ground. Using the band-gap characteristics of the mushroom walls, the four-element SIW CBS MIMO antenna system, where-in the edge-to-edge distance of the antenna elements is 0.024 λ (λ is the wavelength in free space at 2.42 GHz), achieves extremely high isolation of 40 dB between the elements throughout the operating frequency bandwidth of 2.396 GHz-2.445 GHz, the envelope correlation coefficient (ECC) is lower than 0.02 across the operating bandwidth accordingly.