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Uncertainty of the time-domain corrected data

Question asked by hudla on Dec 19, 2007
Latest reply on Dec 20, 2007 by Dr_joel
My question deals with the calculation of the measurement uncertainty with using the time-domain (TD) option of VNAs (in my case 8510C or PNA). There exist sophisticated ways how to calculate the measurement uncertainty in the frequency domain (FD) and the main sources of the uncertainty are usually known.
On the other hand, there exist ways how to improve the results obtained in the FD with use of TD techniques and how to minimize several systematic errors (either directly in VNA, or by subsequent computer postprocessing). The question is, what is the uncertainty of such TD corrected data when I know the uncertainty of the data obtained in FD?
For me there are too many unknowns in the process: to calculate the uncertainty resulting from the DFT algorithms, I have to know the A/D converter quantization uncertainty, effective number of bits, parameters of the window used for gating etc. Also I have problems with the conversion of the uncertainties between TD and FD, since they are correlated in a complicated manner.

Does anyone have experience with that? I have found only works dealing with TD correction techniques of data from FD, but no uncertainty analysis of such process.

Martin Hudlicka
Czech Metrology Institute
Prague, Czech Republic