Eeff --> Er of CPW T-Resonator

I have a coplanar T Resonator (a quarter lambda) . I got the measured S-parameter by measuring the two T arms (2-port measurement).
How can I obtain the Er of the substrate from Eeff information ?

jct

You will have to do an EM-simulation of your filter. Use your first guess of eps_r for the substrate in the simulation. You can just come up with a number or if you want, guess it with an analytical CPW formula.

The you can compare the resonance frequency of your simulation to your measurement. Now adjust the esp_r of the simulator and rerun until the rsonances match.

After a just a couple iteration you should have eps_t.