Mutual coupling reduction of compact four-element MIMO slot antennas using metamaterial mushroom structures

In this paper, the mutual coupling reduction of four-element substrate integrated cavity-backed slot (SICBS) antenna system based on two types of metamaterial mushroom structures are studied. In the first case, a double-layer mushroom wall is vertically positioned in between the SICBS antenna elements. In the second design, five double-layer mushroom cells are horizontally positioned above the SICBS antenna elements for mutual coupling suppression. The mushroom structure-loaded four-element SICBS antenna systems achieve ultra-low inter-element mutual coupling of -40 dB over the bandwidth of 2.39-2.45 GHz and 2.386-2.43 GHz (|S11|<;- 10 dB), respectively.