As I know, CST has no such possibility. But you can use indirect methods to determine a capacity. In a simple case, with two patches you can make the analytical calculation of capacity by using formulae for plate capacitor.

If you have some sophisticated geometry, you can replace your patches by ports and use CST schematic tab trying to find corresponding capacity values with the optimizer or manually.

Attach two ports on the gap, analyze the S parameters and then open a session on Design Studio where you will compare the S parameters just computed with a capacitor whose value you will tune so that both responses are similar, on the freq range youve got interest in. The last step can be done also in Matlab.

thanks Marcelo B. Perotoni for your answer what equation can i use to find it

thanks Egor Kretov for your answer but please what formula plate capacitor

Hello,

Use lumped port to calculate capacitance. As in some EBG structures, Capacitance =( (width of patch)*(epsilon)*(epsilon+1))/(pi).

See the attached paper.

Thanks,

Either use an electroquasistatic solver. There is one in Ansys (Q3D). I bet there is an alternative tool in CST.

or

Add ports to the structure, simulate the S parameters, convert to Z or Y parameters. The -Y12, for instance, appearing in the series branch of the PI representation of the Y parameters can approximate the admitrance of the capacitance.