• UnknownEditor
    48
    Does anyone have any experience doing a VNA calibration at an SMPM interface? The only cal kit I see for sale uses TRL and LRL airlines, not sure I want to get involved in that. Is there an SOLT kit out there? Or is it acceptable to calibrate to 2.92 or 2.4mm interface and add adapters afterwards?

    Thanks in advance,

    Steve
  • madengr
    15
    I’ve used through-hole, vertical mount GPO at X-band. In that case, I just calibrated at 3.5 mm and used the adapter. I then tweaked the matching network on the PCB for good return loss. I was looking back into an isolator, so didn’t need a load.

    If you have enough distance (on the PCB) between the GPO and the next discontinuity, maybe use time domain mode to measure the GPO, or gate it out.

    If you know the GPO has good return loss (which you can do with time domain), and can get a short circuit established after it, then use port extension to get a phase corrected measurement. Though YMMV with port extension; I put a marker at the frequency I’m most interested in, then rotate the delay for an exact short at the marker. The phase typically diverges above and below the marker frequency, but at least I know the phase is correct at that one frequency.

    GP3O and even WFL are “good” through 60 GHz, but all that means is they don’t mode. The WFL has piss poor return loss even at 2 GHz.
  • acl
    1
    Hi Steve,

    We haven't found anything apart from the Micro-Mode TRL/LRL kit.
    We have always calibrated as close as we can to the gppo adapters.

    If you are using non-threaded gppo's then I don't know how good your cal would be anyway, as the connection is not super consistent.

    Thanks,
    Andrew
  • UnknownEditor
    48
    Thanks to you both

    I think I will stay away from trying to calibrate to that interface, and somehow model the adapter and subtract it off as an S-parameter file or maybe just a linear model. I am no expert on time domain but it seems like when you gate out a reflection the improvement sometimes too good to be true... This is not for device characterization, more like an acceptance test. A good design should have plenty of room for error, right?

    I think about an acceptance test at a previous employer where phase tracking was needed over wideband. The operator was trained to misalign the GPO until it met the spec, then hit the save button... yikes.

    Steve
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