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How can I best use an 85052B 3.5 mm kit for SMA devices?

Question asked by drkirkby on Sep 25, 2013
Latest reply on Sep 30, 2013 by drkirkby
I've got an 85052B 26.5 GHz standard calibration kit. The coefficients for the 85052B 3.5 mm kit are in the firmware of my VNA. Taking the example of the opens, I see: 

C0=49.433, C1=-310.13, C2=23.168, C3=-0.15966 offset delay = 29.243 ps etc

I understand what all those mean. 

These are very similar, but *not* identical to those given for the PNA at 

http://na.tm.agilent.com/pna/caldefs/PNA/85052B.htm

The firmware (version 7.74) for my 8720D use an offset delay of 29.243 ps, and in that page it shows 29.2 ps for the PNA, so there is a difference of 43 fs, which is pretty small, although I'm puzzled why it exists. Anyway, that is a minor issue. 

Now to the more important issue. 

Naturally I sometimes use SMA devices, and I know there is some electrical mis-match between SMA and 3.5 mm, which one could resolve by de-embedding, although I've never actually looked into it. But is there a simpler way of measuring SMA devices? 

Looking at the HTML page for this 85052B cal kit with the *PNA* series, 

http://na.tm.agilent.com/pna/caldefs/PNA/85052B.htm

I see a lot more standards than are in the firmware of my 8720D. For example, standard #9 in the PNA list has these *very* different capacitance coefficients for "3.5 mm/SMA male open"

C0=5.9588, C1=-11.195, C2=0.5076, C3=-0.00243

The C0 term has changed by a factor of more than eight, from 49.433 fF to 5.9588 fF. 

I'm *guessing* one should use a different set of coefficients if measuring SMA devices, rather than 3.5 mm devices, and *perhaps* that HTML page has the magic numbers to use. Am I right, or have I "lost the plot"?

If a different set of coefficients are preferable when measuring SMA devices, I would like to use them. I realize the 8720D is limited to 8 standards, so I can't define as many as on an 8510 or PNA, but there is nothing stopping me defining another cal kit for SMA, IF I only knew exactly how to interpret those numbers given for the PNA

How do I interpret those values for the PNA. For example, what exactly does standard #9 ("3.5 mm/SMA male open") here

http://na.tm.agilent.com/pna/caldefs/PNA/85052B.htm

actually mean? Even more complicated, what exactly does standard #18 ("2.92 mm/SMA female open") mean? 

If for example I wanted to measure an SMA female device with my 3.5 mm cal kit, what are the optimal coefficients to define for the open? 

I expect if I had a PNA, this would be more obvious to me, but I can't help feeling a user cal kit in my 8720D would do the same job. 

Dave  

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