how to calculate ft and fmax by S para or other paras?

I want to get the frequency response and frequency characteristic throutgh equivalent model of the FET or BJT, and describe ft and fmax with them, or get ft and fmax by S parameters or other parameters, does anyone give some constructive advices?
there are many equations in books, but i want to get them with no approximation, and with the equivalent model established myself.

thansk all!
pursue

With s-parameters, you can not find Ft and Fmax.
Ft and Fmax bias dependent and they are calculated or simulated only.
If you know the definitions well, you can extract these from AC simulations.

under the fixed bias condition, the Ft and Fmax is only changed with frequency. with the S parameters under the same bias, and the H parameters can be obtained, then Ft is calculated by H21, is that right?
if this is OK, how can we get Fmax through S parameters!

thanks!

S parameters are only applied for small signal and linear systems. So it cannot tell you Ft or Fmax. Simulation using Spice model may help you.