You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
To properly calculate the group delay, -dphi / (2 * pi * df), the phase must be "unwrapped". Otherwise for large phase shifts (<180 deg) across measurement points, the group delay calculation will be in error. For a non-dispersive DUT like a coaxial cable, high accuracy group delay measurements require such a large frequency "aperture". A df of .3 / delay is recommended. Unfortunately because of this issue my measurements were wrong.
See https://twitter.com/gmagiros/status/1396204275089477636?s=20
This issue also exists in the nanovnav2 and nanovna-saver code.
The python code below demonstrates two ways to properly calculate group delay.
NanoVNA/plot.c
Line 449 in d02db79
To properly calculate the group delay, -dphi / (2 * pi * df), the phase must be "unwrapped". Otherwise for large phase shifts (<180 deg) across measurement points, the group delay calculation will be in error. For a non-dispersive DUT like a coaxial cable, high accuracy group delay measurements require such a large frequency "aperture". A df of .3 / delay is recommended. Unfortunately because of this issue my measurements were wrong.
See https://twitter.com/gmagiros/status/1396204275089477636?s=20
This issue also exists in the nanovnav2 and nanovna-saver code.
The python code below demonstrates two ways to properly calculate group delay.
My method:
Or using the scikit-rf method:
The text was updated successfully, but these errors were encountered: