Hi,

I'm doing 2-port passive measurements with SOLT probe calibrations (PNA 8364B). I'm trying to calculate the measurement uncertainty in transmission S21 measurements. The VNA uncertainty calculator does not have probe cal kits, so I cannot use that.

I've seen the 12-error term equations in Agilent application notes (AN 1287-3, Figure 5 and Figure 14) , so I try to use those equations, but the uncertainties I get are unreasonable (~10dB). I'm sure I'm doing something wrong in the procedure. So, please help me clarify some of the following issues.

1) In those equations, are the error terms (directivity, source match, transmission tracking, ....) raw or residual?

2) How can I get the 12 residual error terms? From PNA, I exported 12 error terms through "Cal Set Viewer", and used them in the equations. They seem quite large; transmission tracking term is -12dB at 20GHz. Are they corrected residual error terms or raw error terms?

3) Should I use the measured S21 from VNA to calculate the uncertainty? Or do I have to calculate S21_a first using equations in Figure 5, then calculate the uncertainty using Figure 14 equations?

4) For the measured S21 saved from VNA, is it S21_m or S21_a in those equations?

Please advise me if there are other ways to find the uncertainty.

thank you very much.

I'm doing 2-port passive measurements with SOLT probe calibrations (PNA 8364B). I'm trying to calculate the measurement uncertainty in transmission S21 measurements. The VNA uncertainty calculator does not have probe cal kits, so I cannot use that.

I've seen the 12-error term equations in Agilent application notes (AN 1287-3, Figure 5 and Figure 14) , so I try to use those equations, but the uncertainties I get are unreasonable (~10dB). I'm sure I'm doing something wrong in the procedure. So, please help me clarify some of the following issues.

1) In those equations, are the error terms (directivity, source match, transmission tracking, ....) raw or residual?

2) How can I get the 12 residual error terms? From PNA, I exported 12 error terms through "Cal Set Viewer", and used them in the equations. They seem quite large; transmission tracking term is -12dB at 20GHz. Are they corrected residual error terms or raw error terms?

3) Should I use the measured S21 from VNA to calculate the uncertainty? Or do I have to calculate S21_a first using equations in Figure 5, then calculate the uncertainty using Figure 14 equations?

4) For the measured S21 saved from VNA, is it S21_m or S21_a in those equations?

Please advise me if there are other ways to find the uncertainty.

thank you very much.

mostly residual, except S21. A very good estimate of S21 uncertainty is SMresidual*LMraw+LMresidual*SMraw, where SM is source match and LM is load match.

The calset view always shows the raw error terms. Determining residual error terms is a really difficult problem.

For S21, the uncertainty for the most part does not depend upon the value of S21, as long as it is not so small that noise floor adds in.

If correction is on, it is S21_a, if correction is off, it is S21_m

You must check with your probe manufacturer to find out what the residual error of the cal substrate is. There are some "long-line" techniques that can let you estimate it. Google something like "estimating source match from ripple" to see if you can find something. For the most part, the load will set the error in source match, load match and therefore S21.