Estimation of the Cross-Correlation Green’s Function for MIMO Systems

In this paper, we demonstrate the possibility of analytically evaluating the frequency-domain Cross-correlation Green's functions (CGFs), which helps in estimation of far-field correlation in MIMO systems from the antenna current distribution. We propose a robust truncated series-approximation formula to calculate the CGF tensor components, thereby eliminating the requirement of numerically integrating complex exponential functions. Using examples involving vertical dipole pairs, we highlight the inter-connection between the number of terms required in the truncated series-approximation and the normalized inter-element spacing. The proposed analytical evaluation scheme will facilitate integration of these CGFs into optimal synthesis of MIMO antenna systems.