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Calibrating VNA for measurement of 7mm/3.5mm DUT

Question asked by residentAlien on Oct 5, 2011
Latest reply on Oct 10, 2011 by residentAlien
Hello all,

I have a DUT with one port being a 7mm (APC-7) connector and the other port being a 3.5mm (SMA) connector which I want to measure. The problem is that I really can't understand how to do this and still get accurate results.

I've read several application notes from Agilent on adapter removal techniques for their VNAs, but I always end up with getting a scenario which I can't solve (a scenario that I believe won't give the desired accuracy).

I.e. if I start with the following:

VNA-cable-[7mm]-(End port1) (End port2)-[7mm-to-3.5mm male adapter][3.5mm female-to-7mm adapter][7mm]-cable-VNA

and perform a 7mm calibration, the next step following i.e. page 14 in is to perform a 3.5mm calibration when I have the following setup

VNA-cable-[7mm][7mm-to-3.5mm male adapter]-(End port1) (End port2)-[3.5mm female-to-7mm adapter][7mm]-cable-VNA

however, here I have one port with female and one port with male connectors, which I believe have different reference planes inside the cal components - and will therefore introduce an error in the calibration.

Trying to do the 3.5mm calibration first, I end up with the same problem; so then I wonder how on earth I should do this in order to get accurate measurements?

Does anyone have any good tips/hints?

Best regards