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TRL Calibration Problems

Question asked by RandyC on Apr 18, 2011
Latest reply on Apr 20, 2011 by Dr_joel
I would like advice on some TRL cal problems I am having.  I have a set of 8mil R4003 boards that have Thru, Delay, and Short on them for calibration, and when I go back and measure them after cal, the short appears to have loops or kinks in it.  The phase is not monotonic.   These same features seem to show up as strange features in measurement of my DUT also.  What is this likely due to? 

1) Line width (Z0) differences between standards due to tolerance of the PCB manufacture?
2) Cal kit setup?  I built a cal kit using LRL auto, ref at center of thru, Z0 of line, single 1.3mm delay line (8-60GHz), zero length thru, substrate via at ref plane for reflect.
3)  Physical structure of standards?  See attached images.
4)???
Thank you,
Randy  

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