Impact of total efficiency of multiple element antennas on diversity and capacity

For analyzing the effect of antenna efficiency on MIMO communications, it is convenient to express the total efficiency of a multiple element antenna (MEA) as a diagonal matrix of the total efficiencies of the embedded elements. Using this, the impact of the MEA total efficiency on the diversity gain and information theoretic capacity is formulated and demonstrated. A diversity order and a capacity order are defined from an equivalent number of idealized (lossless, uncorrelated, uncoupled, equal power) branches, similar to the concept of degrees of freedom. This equivalent branch metric allows the performances of different MEA designs to be compared.