how to calculate transformer

I build two coils in CST 2009,the two pins of the primary coil was set as discrete port,calls port1,the two pins of the secondy coil was set as discrete port,calls port2,then I simulated two coils in CST,and I got s11,s21,s12,s22,How to get the coupler coefficiency parameter k and the power transmassion efficiency,or power transmission efficiency using S parameters?
I set waveguide port too.the two pins of the primary coil was set as waveguide ports,calls port1 and port2;the two pins of the primary coil was set as waveguide ports,calls port3 and port4;after simulating,I got s11,s22,s33,s44,s12,s13,s14 and so on. How can I get the coupler coefficiency parameter k and the power transmassion efficiency,or power transmission efficiency using S parameters?

Is it coefficient of mutual coupling that you are interested?

yes,Thz

see the paper entitled: "substrate effects in monolithic rf transformers on silicon" author: Kiat T. Ng
The Gmax or Kim.

what's about mutual coupling caculation for 4-port transformer?

The mutual coupling coefficient between two coils of a transformer is mechanically depended so there isn't any method to ampricaly calculate it...
It's measured only..
But for planar transformers, it's possible to find the coupling coefficient by simulating the structure.

thanks BigBoss, but I mean that how to calculate mutual coupling coefficient from S-parameter (of 4port transformer).

Could you please suggest me some documents or equations to find it from S-parameters? I already simulated 4-port transformer but I don't know how to find the mutual coupling coeficient?