Discussion Forum

Hello,

I would like to compute, among other parameters, the impedance in a PCB, for a strip line between two ground shields. An approximation can be use to compute this impedance given by:

where and t are respectively the distance between the strip line and the shields, the strip line width and the line thickness, as shown on Figure_1.png.

I would like, for a given set of parameters, that COMSOL returns the computed impedance of this object. The idea is to compare it with the impedance given by the above formula and then try to optimise the PCB dimensions.

I have implemented this in COMSOL following several tutorials, forum posts and blogs but I never got a satisfying impedance results (imaginary value, NaN, Inf or 0). I was expecting the impedance could be easily computed such as the capacitance that is given by C11.

Implementation: In the strip line a current of 2uA circulates. The two shields are grounded. They are into an insulator with . For other studies, I will work with emw and frequency variation, but to me this impedance computation does not depend on the physics type as it only depends on PCB dimension (maybe I am wrong here). That's why I tried several physics and I woked with a stationnary study. My model is attached below.

What am I doing wrong?

Thanks a lot in advance for your response, help and time.

Cheers,

Marina