On the Covariance Matrix and Diversity Performance Evaluation of Compact Multiport Antenna Systems

In this communication, we present a new electromagnetic methodology that determines the covariance matrix of compact multiport antenna (MPA) systems at the early design stage. Further insight into this field is provided, as contrary to existing methodologies, it rigorously relies on the reciprocity principle of MPA systems. Thus, the impact of propagation environment, termination conditions, and MPA radiation characteristics as independent factors affecting performance is physically incorporated. Provided the availability of mathematical expressions for the cumulative distribution function and probability density function of received signal-to-noise ratio (SNR), performance can then be analytically studied via the diversity antenna gain (DAG) in terms of: 1) SNR enhancement at a specific outage probability (OP) level (that is DAG-OP) and 2) average SNR reduction for achieving a specific average bit error rate (BER) (that is DAG-BER). Illustrative examples with performance evaluation of compact MPA systems are presented. The adopted diversity technique is the transmit antenna selection/maximal ratio combining, which is analytically studied employing realistic MPA systems for the first time. Comparisons with existing published results further demonstrate the validity and usefulness of the proposed methodology.