how to account for mutual coupling between antenna array elements

How is it done in HFSS, for example? Do we look at active impedance value and set the input impedance of each of the elements to match the active impedance? Please attach examples.

Thanks.

u can find some helpful equation in here
Bandwidth Enhancement of Antenna Arrays UtilizingMutual
Coupling between Antenna Elements
by MinWang , WenWu and Zhongxiang Shen

Hindawi Publishing Corporation
International Journal of Antennas and Propagation
Volume 2010, Article ID 690713, 9 pages
doi:10.1155/2010/690713
Wang , WenWu and Zhongxiang Shen