Application of Cross-Correlation Greens Function Along With FDTD for Fast Computation of Envelope Correlation Coefficient Over Wideband for MIMO Antennas

In this paper, the concept of cross-correlation Green's functions (CGFs) is used in conjunction with the finite-difference time-domain (FDTD) technique for the calculation of envelope correlation coefficient (ECC) of any arbitrary multiple-input multiple-output (MIMO) antenna system over wide frequency band. Both frequency-domain (FD) and time-domain (TD) postprocessing techniques are proposed for possible application with this FDTD-CGF scheme. The FDTD-CGF-TD scheme utilizes TD signal-processing methods and exhibits significant reduction in ECC computation time as compared with the FDTD-CGF-FD scheme, for high-frequency resolution requirements. The proposed FDTD-CGF-based schemes can be applied for accurate and fast prediction of wideband ECC response, instead of the conventional scattering parameter-based techniques which have several limitations. Numerical examples of the proposed FDTD-CGF techniques are provided for two-element MIMO systems involving thin-wire half-wavelength dipoles in parallel side-by-side as well as orthogonal arrangements. Furthermore, examples of two-element MIMO systems involving multiband LC resonator loaded dipoles and pattern-diversity antennas using parasitic elements are also included. The results obtained from the FDTD-CGF techniques are compared with results from commercial electromagnetic solver Ansys HFSS, to verify the validity of proposed approach.