AnsweredAssumed Answered

TRL Confusion Eliminated - Once and For All

Question asked by VNA123 on Jul 31, 2015
Latest reply on Aug 13, 2015 by Dr_joel

When I do a TRL PCB/Wafer Cal I do this:

Right now, I'm trying to do a TRL calibration for an 42.5Ohm PCB Test Fixture.

Say, secondary 1 is (0.2Ghz-1GHz), secondary 2 is (1Ghz-5Ghz), and secondary 3 is (5GHz-25GHz). I type this information along with the time delay into the keysight VNA for thru/line measurements when creating the trl kit. 
I add a short/open, a load, and a 2xthru(Primary). For these, I only put in the bandwidth. 2xthru Primary (0Ghz – 25Ghz), short (0Ghz-25Ghz), open(0GHz-25GHz), Load (0Ghz-0.2Ghz) are set in the cal kit for the vna. 
I then set the calibration reference Z0 to “Line Z0” and the Testport Reference Plane to “THRU Standard”, leave LRL line auto characterization checked, and add the appropriate standards to the proper classes (below).

TRL THRU – Primary
TRL Reflect – Short/Open
TRL Line/Match – 3 Secondaries & a Load

My Question is simple:

1) I have NEVER changed my system Z0 away from 50Ohm. All the coaxial sma connectors are 50Ohm, All my traces are 42.5Ohm. 
2) I have NEVER changed my standard impedances (OPEN, PRIMARY, SECONDARY1, SECONDARY2, SECONDARY3, LOAD) away from 50Ohm
*3) What are my S-Parameters Referenced too?!?!? Why Do I ask? Because when I learned about port nomalization I said "Oh I'm doing this wrong". So I went and did the entire cal over and changed the statndards impedances to 42.5Ohm. Guess what? SAME S-PARAMETERS. So confused. Dr. Joel, please help me not be confused any longer. When I set the calibration reference Z0 to "Line Z0" is that literally going to set it to what i typed in the impdance box when creating the kit? Or is it measured?*

_*Goal of everything:*_

1) Perform Cal Properly for 42.5Ohm Fixture
2) Get S-Parameters that are reference to 42.5Ohm / 85Ohm Differential
3) When I usedPLTS to IFFT my S-parameters, I want it to read 85Ohm, not 100Ohm (which is what happens).