The correct application of total active reflection coefficient to evaluate MIMO antenna systems and its generalization to N ports

Several papers published by prestigious Journals on Antennas and Microwave Techniques have disseminated misconceptions about total active reflection coefficient (TARC), a meaningful metric to characterize multiple‐input multiple‐output antenna arrays, and the misapprehension has been spread over the years. In this article, an extrapolation to calculate TARC for N‐antennas systems is derived and applied to published results for illustration purposes. Moreover, the inaccurate and correct TARC equations are put in context by means of its physic and mathematical insight, demonstrating the divergence of results when the interport RF isolation is comparable or higher than the port matching. The importance of assessing multiantenna systems using TARC is explained.