Radiation conductance of an antenna out of S-Parameters

Any one knows how to extract the radiation conductance (which should be is mS) out of a Scattering parameter measurement (S11) for an antenna?
Thank you for helping :)

Well solved this quastion :)..
The radiation conductance of an antenna is the real part of the antenna admittance. So just converted the S11 to Y-Paramter

That's not necessarily correct. If there's any losses in the antenna itself (besides radiation), they'd also show up in the real part of input admittance.

There's no way that I'm aware of to separate the two with just the S-parameters.

I totally agree with this argument. Real part of Y11 contains not only radiation conductance but also loss conductance.

I think you can run an EM simulation in comparsion with the measured result. In the simulation you can turn on and turn off the loss parameter, from that you can evaluate the radiation conductance.