FEDEVEL
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Domagoj , 09-12-2023, 09:34 AM

Has anyone encountered an impedance variation of a coplanar waveguide with ground plane similar to this one on the image?
It is a 4L PCB with CPWG on L1, reference plane on L2, h = 0.148 mm, w = 0.25 mm, g = 0.2 mm, Dk = 4.6.
I can't explain the sudden jump in impedance from ~30ohms at around 2.2 GHz to ~60ohms, and then it stays at that higher value.

QDrives , 09-12-2023, 08:25 PM

Is this a:
- measurement
- simulation using 3D field solver
- calculation tool
- other?

Domagoj , 09-14-2023, 06:33 AM

Measurement, i.e. calculated from S-parameters by using the lossy transmission line model.
The calculation was confirmed using a known good through line on a different PCB.

Domagoj , 09-14-2023, 06:35 AM

And also confirmed on two frequencies using this method https://hamwaves.com/zc.measuring/en/index.html

Robert Feranec , 09-21-2023, 12:08 PM

was the cable calibrated correctly?

Domagoj , 09-21-2023, 01:52 PM

Yes, OSLT calibration was executed.