Errors in Current S11 1-Port Measurement Calibration

By: Grant Heileman05/13/2015

I would like to start off by stating that I have little confidence in the precession of the VNAs current tuning. I say this because after following the same calibration procedure several times I have noticed that what I believe to be incorrect calibrations occurs about 2 out of 5 times. I have been told that this can be fixed but requires offsite attention. Along side of this there is the issue of a different setup of connectors being used for calibration and measurements. This inconsistency is due to lack of a complete 3.5 mm calibration kit. The 3.5 mm Cal. Kit in Dr. Christodoulous lab (HP 85052C) is missing the airline for 7-32 GHz and thus cannot be used by the VNA to calculate transmission coefficients. It is for this reason and through the advisement of others that I have attempted to take the measurements of our board and the STWUEE chamber after calibrating with the 2.4 mm kit (HP 85056D). I have deduced that, as expected, there is an inherent error contributed by the switching of connectors. After discussing the setup of the equipment and the exact areas of interest I will discuss some of the measurements I took that demonstrate this error.

The calibration and measurement system is as follows; and further pictures are contained in the appendix for clarification.

HP 8720D Network Analyzer 50MHz-20GHz. This is the first area of interest I dont know how to make sure that the VNA is tuned properly without taking it into the offsite technician or comparing base measurements with another VNA that we secretin is precise.

Port 1

Pasternack Enterprise Inc. VNA test cable kit DC to 26.5 GHz. A grey hair-tie was placed around one of the cables to tell them apart during troubleshooting.VNA cable to 3.5 female

Grey hair-tieVNA cable to 3.5 male

Agilent 2.4 mm Calibration Kit, borrowed from Dr. Christodoulous lab.Note: There are two non-standard connectors in his kit, a 3.5 mm male to 2.4 mm female and a 3.5 mm female to 2.4 mm male. The later of which is currently being used in another project. 2.4 female to 3.5 male

The VNA can now be calibrated to the 2.4 mm kit standard. In the appendix a procedure is listed for calibration/saving data to the internal floppy drive and can be found here.https://www.dropbox.com/home/S11%20Measurements?preview=VNA+Calibration.docx Having successfully calibrated the VNA we can confidently move onto the measurements; however, it is at this that point I wouldnt mind another VNA to check our calibration against. As we continue from this point we deviate further and further from the calculated calibration constants so it is imperative to know with certainty whether or not the VNA and calibration kit are working as expected.

The 3.5 mm to 2.4 mm connectors are now switched with their respective 3.5mm to 3.5 mm connector and the board or the STUWEE chamber is connected.