#### sandbo

##### Newbie level 6

I am trying to extract the capacitance of an interdigitated capacitor along a CPW waveguide.

I have been trying different ways, from using Y-parameter by modelling the the thing as a pi-network, however I didn't get something reasonable with the calculated capacitance being heavily frequency dependent, which I guess the inductance of the line played a role.

Then I turned to use surface integral method to find the capacitance,

that is by setting a voltage source of 1V between two sets of fingers, and then calculate the surface integral of one of them, multiplying with permitting, finally divided by voltage (1V) I should get the capacitance.

I am however getting a value larger than the accepted value by many other papers; I realized that I might be integrating over field that is not contributing to the capacitance.

May I know if there is a more straight forward way to find the capacitance?

I am a bit desperate as this has really spent me a long time.....

Many thanks!