Cavity filter - how to calculate coupling factors from S-parameter simulation?

Hello everyone,

I am trying to design combline cavity filters according to Puglia 1 Puglia 2. I can calculate lowpass g-goefficients and coupling factors for my filter. Now I am trying to figure out how to get from the coupling factors to the geometry of an actual coupling aperture.

Puglia 2 says to simulate two symmetrical coupled resonators (which I did in HFSS) and determine the self-capacitance

and mutual capacitance

from the simulation. It is unclear to me how to determine Cg and Cm. From the HFSS simulation I get S/Y/Z-parameters. How can I calculate

and

? Any hints?

Thanks in advance
Sebastian