How do I overcome this type of data break in between my TRL calibration standards? This mostly happens on my second line transition from LINE1 to LINE2 when measuring my DUT's.
The break is because your two line standards are NOT the same impedance. Please make them the same impedance. If you cannot make them the same impedance, measure their impedance and update the calibration kit with the proper impedance.
Hello Dr. Joel,
Thanks for the response. The lines are etched on the exact same substrate with the exact same GCPW ratios along with the same connectors. How can I check the differences in impedance, measure both S11 and overlay on a Smith Chart?
I see now. Is there where I adjust it on the Calkit?
That’s the value you would change. The most proper way would be to do a time domain transform and look at the reflection coefficient in the step mode and compute the impedance from that. OR, a simple way is to take the second line, adjust the impedance up 1 ohm and repeat the cal…see if the step gets bigger or smaller. Then iterate until the step disappears. The s11 of the line includes many effects besides the line impedance, most predominantly the line length and the residual load match. The time domain transform doesn’t have such issues. You can see the details in pages 274-277 of my book.
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