Characteristic Z of coplanar waveguide

[peanutnjelly]

Hello.
I'm using free saturn PCB toolkit to determine characteristic impedance of coplanar waveguide. But I get strange results.
In my opinion the impedance of coplanar waveguide should match the impedance of microstrip line when distance between GND on top and line goes to ∞ and the rest of distances are the same.
But the calculator say's that impedances are not equal.

Results matches the online calculator:
https://chemandy.com/calculators/coplanar-waveguide-with-ground-calculator.htm

I gues that equation for coplanar line is only valid for small distances W in comparison of h and S.

 

[vfone]

You are right. I think something is wrong there. For example for CPW we get about 3 ohms impedance variation for distances of the top ground to the line, between 20mm and 100mm. When for such distances should be practically no big impedance variation, because both distances are greater than 3x line width.

 

[FvM]

I gues that equation for coplanar line is only valid for small distances W in comparison of h and S.

As clearly mentioned in the simulator description...

 

[peanutnjelly]

entschuldigung, danke :smile: