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Calibration with Fixture Simulator "ON" Topology "Bal-Bal"

Question asked by RomanB on May 26, 2010
Latest reply on May 27, 2010 by RomanB
Hi everybody,

I'm trying to calibrate my E5071B while the fixture simulator is "on". The reason is, I want to measure a DUT, which has a Twinax plug. Therefor I connected the ENA with Type-N connectors to my Type-N--Twinax interface (selfmade). Now I'm trying to get my reference layer at the output of my Type-N2Twinax interface. I'm using two of those interfaces, so all four ports of my ENA are in use. What I did:

  • While nothing is connected, I did (in the common 4-Port Calibration) the Open-Calibration for all ports (Open[m])

  • After that I made my Balanced-Calibration. Therefore I connected the first pin of the output of my first  Type-N2Twinax interface through a selfmade-SMD-50-Ohms-plug with ground. This has been done for all four ports.

  • The Short-Calibration has also been done with a selfmade plug which connected every port (pin) with ground (one after another)

  • The Transmission-Calibration was done with a shielded, short cable with Twinax plugs on it.
To validate my calibration I checked the Sdd11 parameter while having all ports open (at the Twinax-Box) --> No attenuation, which sounds good to me. However when I connected my 50 Ohm resistor plug (it is really accurate) I have only an attenuation of ~8dB. I expected something between 40 and 50dB. The measurements taking place between 300kHz and 1GHz.

I guess the might be an error in reasing. It is almost impossible that the used material is so bad.

Do I observe the right parameters? Is Bal-Bal working for my experiment?

Would be great if somebody has an idea.

Best regards