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VNA Uncertainty Spreadsheet

Question asked by Frank on Feb 13, 2007
Latest reply on Feb 16, 2007 by daveb
About the Agilent VNA Uncertainty spreadsheet, a couple of questions:

The sheet appears to yield higher-than-expected uncertainty magnitudes. For example,  uncertainty of S21 that is calculated with the sheet (for measurements of normal, not pathological, devices) appears to depend little on the VNA model,the  cal kit selection, averaging or video bandwidth, or initial estimates for S21 and S11.   There is a dependence on frequency band, of course, so let's say  we are measuring at 2.4GHz, for example.  The lowest uncertainty magnitudes in dB fall between roughly 0.10dB and 0.15dB, which seems larger and it seems more irreducible than I expected.  Perhaps I missed it but are these 2-sigma numbers?  For no particular reason, I would expected less than 0.05dB under optimum conditions with the best VNAs.  Am I operating the spreadsheet incorrectly? Is there detailed background available for how this sheet computes its results and some guidance on selection of parameters?