VNA400: questions about calibration in through mode

Hi team,
we recently bought the VNA400 together the Maury Microwave 2.92 mm cables and the calibration kit SOLT 8770CK by Maury Microwave.

When i run the calibration, the open, short and load results are correct for both ports, but when i reclose the port 1 and the port 2 with the thorough adapter (P/N KF-KF50 by Mini-Circuits) to perform the thorough calibration, the S21 parameter is not to reset to 0 (see the attached images).
Why?
Can you help me?

Thank you in advance.
Best Regards,
Matteo Ricci

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In the final picture with the through measurement, the status bar indicates that only the factory calibration is loaded. That would tell me that your 2 port cal is not currently applied. Are you finishing all steps of the calibration, including saving the calibration file prior to making this measurement? Once your calibration is finished and applied, you should see your through measurement normalized.

Hi Andrew,

thank you for the answer.

when i finished the calibration i didn’t save the relative file, so the S21 parameter was not set to 0. Saving the configuration file, the S21 parameter is set to 0.

I have another question:i have to measure a dut with a gain of about 70 dB. To be able to perform this measurement i need to insert a fixed 50 dB attenuator at the output of port 1. How can I include the presence of the attenuator in the calibration setup so that the S21 parameter that I am going to measure is exactly equal to 70 dB?

Thank you in advance,

Matteo

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[Andrew]

Hi Matteo,

I made some suggestions via email, were you able to test those yet? In both of my suggestions, the attenuator would not be part of the cal, but would be inserted afterwards and compensated using one of the techniques below.

The problem with having the attenuator in during the cal is that you will drive the signal into the noise and the unit will not be able to make a good cal.

Here is the main contents from that email.

Port extensions would likely work, there is both controls for setting a typical path loss curve and a fixed DC offset (for narrow spans or coarse measurements). In this scenario the attenuator would be inserted post calibration.

Deembedding would be a more accurate approach. Do the cal without the attenuator. Then insert and measure the full 2 port s-params of just the attenuator. Save the measurement as an S2p file, and use that file for deembedding.

• This reply was modified 6 months, 3 weeks ago by Andrew.
• This reply was modified 6 months, 3 weeks ago by Andrew.
• This reply was modified 6 months, 3 weeks ago by Andrew.

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