Why is the THRU standard on most coaxial SOLT Cal kits defined as 0 seconds?
  • pmiz
    0
    For example I've noticed the 85052D 3.5mm Keysight Cal kit has 0 seconds of offset delay. The Thru standard is actually about 93ps of delay. If I modify the Cal kit THRU definition to 93ps I get accurate S21 group delay. I can't seem to find a great explanation as to why all the Keysight SOLT thru kits define the THRU offset delay as 0 seconds. About the only thing of note was that it may be that way assuming a calibration with one cable end male and the other female, thus the thru is not an inserted adapter but just the two cable ends mated together.

    Thanks, any insight would be appreciated.
    pmiz Options
  • madengr
    1
    Yes, your last sentence is correct. A normal M/F cal uses a zero length thru. Those adapters should be phase matched. If you want to do a M/M cal you could attach a F/M adapter on port 2, do a M/F cal, then swap the adapter to M/M. Any errors introduced are the slight differences between the M/M and F/M adapters.

    There are also adapter removal cals, which fully remove the adapter. The 8510 allowed this by combining two cals sets with the adapter on either port. With the eCal, most of this has been obsoleted with the exception of mixed media such as coax on port 1 and waveguide on port 2.m

    There was actually a method to do two-tier calibration fixture characterization using adapter removal and reading out the error model from the VNA. This is now lost knowledge.

    I believe a non-zero length thru is essentially LRL cal.
    madengr Options
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