How to measure isolation for MIMO antenna from S parameter

Hi

From a given S parameter for multiple antennas (say 2) how do i figure out the isolation? Say for the attach S-parameter it is mention that the isolation is > 17 dB. How do i measure it from figure? Any details technical explanation (any doc,paper) will be helpful.

Thanks in advance.

Regards
farooqui

In your case the isolation is given where S21 line is peaking.
S21 represents the forward transmission coefficient (forward gain or loss), so when measuring the isolation between two antennas, the transfer loss between those antennas is actually the isolation between antennas.
The loss is negative (-17dB) but the isolation generally is given as a positive number (17dB).