Analytical approximation of the time-dependent antenna cross-correlation Green's function

In this paper, the concept of time-domain cross-correlation Green's function (CGF) is introduced to facilitate calculation of envelope correlation coefficient (ECC) for wide-band MIMO antenna systems. Furthermore, a quasi-analytical technique utilizing Taylor's series expansion is proposed in order to reduce the dependency on numerical integrations involving angle-dependent delay terms for evaluating these time-domain CGFs. Finally, some numerical examples involving transient current excitation of infinitesimal dipole pairs (horizontal and vertical) are provided, demonstrating the validity and effectiveness of this time-domain CGF approach for wide-band ECC computation.