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S21 Phase Measurement problems between 8510C Test Sets

Question asked by on Jan 21, 2017
Latest reply on Apr 27, 2017 by bar28

I have a really weird problem that I'm currently tasked to investigate, and have no clue what's going on here.   I'm hoping that someone here maybe has some insight?


Basically, I have two independent 8510C setups...   An Engineering setup, and a New production setup with the following configurations:


Engineering setup -   

      8340A Synthesizing Sweeper, Opt 005, 006, 007

      8510C Firmware C.07.14 8-26-98   Display OPT 010

      8515A S-Parameter Test Set


New Production setup -

      8341A Synthesizing Sweeper, OPT 005

      8510C Firmware C.07.16 12-12-00   Display OPT 010

      8514B S-Parameter Test Set, OPT 2


The problem that I'm having is that with identical Calibration Kits, Test Cables (both ports), and Devices Under Test (DUT), I'm getting large Phase errors on the New production setup when directly compared to data from the Engineering setup....and I don't know which one is correct?  


The DUT has 6-bits which are tested for Insertion Loss and Phase difference from a known reference point at 1232.5 MHz...but we are sweeping across a frequency range from 1175 - 1375MHz with 401 data points (to ensure we're directly gathering data at this specific frequency).  I have attached my latest data run, but have also run 3 other DUTs....which are exhibiting similar "failures".


Does anyone have some thoughts on why I would be seeing large Phase variance/errors?   Thanks