Adjusting to Drift

This contains the scottyspectrumanalyzer yahoo group backup
Post Reply
Sam
Posts: 1151
Joined: Sat Apr 28, 2018 6:49 pm

Adjusting to Drift

Post by Sam » Sun Dec 19, 2010 10:25 pm

In transmission mode, you can compensate for phase drift (and magnitude drift, though that's not much of an issue) by recalibrating. Generally it is not a big deal to redo the line calibration. In reflection mode, OSL calibration requires the use of 3 different standards, so it is a bit more of a pain to re-calibrate. I have implemented, and am still testing, a simple method to adjust to drift in reflection mode.



With OSL calibration, the Open data is used as a reference, in the same way that Line calibration is used for transmission: the reference data is subtracted from the raw data (everything is in db/angle, so subtraction is really division of the underlying values). If you repeat the Open calibration, any change from the previous Open calibration represents drift, some of which may occur in the bridge, but most of which probably occurs within the MSA. If you simply use the new Open data as the reference, in place of the old Open data, you have compensated for the drift.



This means you can periodically update the OSL calibration with a single standard, rather than all 3. This same concept would apply to OSLT calibration, where you can update with one standard instead of repeating all four, and to fancier calibrations, where this could be a massive timesaver. Of course, there are possible changes that this method does not pick up, but it should properly compensate for most things that happen within the MSA.



Sam W.

Post Reply