Grounded CPW

[ncc1701]

I am trying to diagnoise a problem with a CPW board and I need to calculate the impedance and dielectric constant. If you know the via sizes, location, the material, (in this case Rogers 4003), and the dimensions; is there a simple way to determine these pieces of information?

 

[logbook]

The simple answer is no. You calculate the impedance from the mechanical shape and the measured dielectric constant. You calculate the dielectric constant from the measured impedance and the mechanical shape.

You could calculate the dielectric constant from a simple shape and the measured capacitance, but you do need a measurement to start the whole process.

Vias are a miserable addition to the equation and would normally only be soluble using a full finite element analysis.

 

[ncc1701]

OK, I made a typo. I have the dielectric constant of the material and all the gometric dimensions, and I want to calculate the impedance. Is that possible with in a limited degree of accuracy?
Also, I thought that the vias were to keep from generating higher order modes?

 

[felixc]

So you need an impedance calculator program. The sites of some PC fabs offer one. If you Google the terms you will find some.