Decorrelation of a Closely Spaced Antenna Array and Its Influence on MIMO Channel Capacity

The effect of correlation between four closely spaced slot antennas on the capacity of a MIMO system is demonstrated for several different channel scenarios and a practical decorrelation network consisting of a rat-race hybrid is proposed. The effectiveness of this network is independent of the element type or spacing. The properties of the array and decorrelation network are investigated by means of a finite difference time domain (FDTD) analysis. The decorrelation network is shown to reduce the envelope correlation and give improved capacity when the elements are close.