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DiSlord / NanoVNA-D

Firmware for NanoVNA, NanoVNA-H, NanoVNA-H4. Support SD Card, external Serial connection, fast measure, fast exchange vs CPU
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e-delay for s11, s21 #80

Closed owenduffy closed 5 months ago

owenduffy commented 5 months ago

It is commonly the case that the appropriate value of e-delay is different for s11 and s21 measurements.

It would be really convenient if one could specify a s11 e-delay and s21 e-delay so that the presented data for a single sweep is correct for both s11 and s21 derived metrics.

Owen

DiSlord commented 5 months ago

Better add THRU calibration standard compensation (only additional delay) as in LiteVNA Calibration standard option.

PS NanoVNA-Saver allow add this on calibration as I remember (in calibration, Through, Offset delay)

owenduffy commented 5 months ago

Better add THRU calibration standard compensation (only additional delay) as in LiteVNA Calibration standard option.

PS NanoVNA-Saver allow add this on calibration as I remember (in calibration, Through, Offset delay)

I am not sure that I understand you here.

If you mean deduction of the cable used to perform the THRU step of calibration during the calibration measurements so that the VNA is now calibrated with zero delay Port 1 to Port 2, that does not deal with the case that I described.

Consider a calibration with zero delay Port 1 to Port 2, and we connect the DUT with two cables with propagation time 1ns and 3ns, the correct e-delay for s11 correction is 2ns (2* cable1) and for s21 correction is 4ns (cable1 + cable2).

Providing for this means the s11 and s21 data in a single sweep are properly corrected and can be saved as a single s2p file that is correct.

Owen

DiSlord commented 5 months ago

Now possible input edelay for S11 and S21 traces https://github.com/DiSlord/NanoVNA-D/commit/8d3ad9b76d1502a00e3737144a8dc87e2600adc4 You can build firmware or download it from beta test group https://groups.io/g/nanovna-beta-test/message/4582

owenduffy commented 5 months ago

Thanks, that is very responsive.

I have applied for access and will test it ASAP.

Owen

owenduffy commented 5 months ago

I have installed it, cleared config, and found how to access both settings. I will test it on a real scenario in the morning (8 hours away).

Thanks... Owen.

owenduffy commented 5 months ago

Initial testing is good... more in the morning... Owen

owenduffy commented 5 months ago

I have done one practical test where the DUT was a A/B coax switch, test jig e-delay 3ns and 2.205ns. It worked as it should, s21 phase reconciles with physical path length, s11 looks good. I will write the test up in a blog article to show the usefulness of the facility.

I browsed the commit, there were a lot of small changes, and you achieved that very quickly, thanks for your fine effort, very well done.

Owen