The effect of mutual coupling on capacity of 4-element squared antenna array MIMO systems

The channel capacity of an MIMO (multiple input multiple output) system is affected greatly in the case of a compact array configuration by antenna array element mutual coupling (MC). In this paper, we propose a 4-element squared antenna array (SAA) which is considered to be the transmit or receive antenna array due to its symmetric structure instead of linear array. As the beginning of researching this specific SAA configuration, a precise expression of MC, mutual impedance, is firstly derived in this document according to basic antenna theory, next, combined with the equivalent MC network, the effects of MC on the spatial correlation and the average receive power of each antenna array element are investigated; at last, we analyzed and compared the effects of MC on the final channel capacity of SAA and traditional linear array. Theoretical analysis plus numerical simulations are presented to conclude that this symmetric SAA can provide quite stable channel capacity than that of the conventional linear array.