The formulas of MEG using S is accurate for high radiation efficiencies. The general formula of MEG vector is diag(Λ)/Γ0 using the research found in parenthesis that you can download (https://research.amanote.com/publication/HpzP3HMBKQvf0BhiJa4T/on-the-covariance-matrix-and-diversity-performance-evaluation-of-compact-multi-port).