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Measurement Setup Question

Question asked by elosik on Jun 2, 2009
Latest reply on Jun 2, 2009 by elosik
Hi All,

Let me start by saying that I am a digital/mixed signal guy, with very little experience in RF measurement, so forgive me if these questions sound remedial.

I need to build an automated tester which will be used to measure jumper cable properties, specifically VSWR, Insertion Loss and (occasionally) attenuation. The test fixture has 16 possible connections, which will all go to the 16 available inputs of an RF matrix. The matrix outputs will then go to a network analyzer. Sine the fixture connector is proprietary, there are no cal kits for it. I plan to calibrate the system using mechanical standards at an N-Type cable interface at the back end of the fixture connection. The fixture itself will have an N-Type connector, 2-3 inches of coax, ending at the proprietary connector. After calibrating at the N-Type interface, I will use the network analyzers port extension feature to move the reference plane up to the proprietary connector.

How will this setup (significant cable length, several small discontinuities) and calibration process affect the required measurements? Does this sound like a valid method? I should mention that the measurements will be made at 50MHz.

Also, I saw on a different forum that someone posted "I was trying to measure insertion loss (S22)......". I was under the impression that the equation for insertion loss was IL=-10*log((S21^2)/(1-S11^2)). Is this the same as S22, or was that person simply mistaken? (Or am I mistaken?) 

I appreciate the help guys, thanks!