Impact of Parasitic Patches for Controlling Mutual Coupling and Spatial Correlation in Closely Spaced UWB MIMO Antennas

In this paper, we investigate the effects of placing multiple parasitic patches symmetrically in the feed-section, on the port-to-port mutual coupling in UWB MIMO antenna elements with very close edge-to-edge spacing (0.02λ at highest operating wavelength λ). Ansys HFSS based simulations confirm that by strategically tuning these patch dimensions, one can achieve average 6- 8 dB mutual coupling reduction in desired high frequency bands around 6.8 GHz and 9.4 GHz, without adversely affecting the impedance-matching/VSWR performance. Furthermore, for the first time in such UWB monopole systems, we determine the envelope correlation coefficient (ECC) in realistic Gaussian/Uniform propagation scenario for a wide range of elevation angles and angular spread of incoming signals, thereby demonstrating the intrinsic connection between port-to-port coupling and far-field spatial correlation performance.