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How bad would a calibration to 20 GHz be using a 9 GHz 3.5 mm cal kit?

Question asked by drkirkby on Jan 25, 2013
Latest reply on Jan 27, 2013 by Dr_joel
In the thread "Coefficients of fringing capacitance polynomial", where "Frequency Lover" only has a 6 GHz VNA without the TDR function, I offered to try to measure his PCB with my 20 GHz VNA which has the TDR function. 

Then later Joel said his board needs a 20 GHz VNA, which means I'd be stuck as I only have a 9 GHz cal kit (85033E), which only has a fixed load (no sliding load). But I wondered how bad this would be. 

Looking at the fringing capacitance coefficients of the opens in my 9 GHz 85033E cal kit, I note they are the same as in the 26.5 GHz 85052B cal it. (C0=49.433, C1=-310.13 C2=23.168 C3=-0.15966). That sort of leads me to believe they are almost certainly the same parts - perhaps the 9 GHz ones are rejected 26.5 GHz ones, but these must be very similar or identical parts. 

Since the 8720D does not allow one to specify inductance values, I would not be too surprised if the offset and/or capacitance coefficients in that VNA vary a bit between the 85033E and the 85052B kits - I have not checked this. But if 

1) I selected the 85052B calibration kit, which is built into the firmware of my 8720D/
2) Used a broadband load to 20 GHz

what sort of performance (or lack of) would be expected?

I was wondering if it could sort out Frequency Lover's PCB issue if I calibrated the VNA to 20 GHz, despite not having a sliding load. 


Edited by: drkirkby on Jan 25, 2013 11:23 PM