"Unknown thru calibration (also sometimes known as SOLR - short open load reciprocal) allows you to do a two-port cal using short/open/load on each port, then an unknown but reciprocal (S21=S12) thru standard between the ports. Some particularly useful applications are when both ends of the cable are the same sex (such as if your DUT is has Female SMA connectors on each port), or an on wafer calibration where the thru line between the probes has a bend or maybe a loop back (for differential probes). In the case of the f-f DUT, after putting on the OSL standards, you can use any kind of f-f adapter, and the cal will complete._________________Joel Dunsmore, Ph.D. Component Test Division Agilent TechnologiesDr_joel"
"Dr_joel noted that the ends of the cables should be same sex (in unknown thru method).Does it mean that also cables and their ends should be same? or on fixture side only?(jacks)"
"In order to get the switch terms, you will need to perform a delta match calibration "
"I'm using an 8364B PNA with option 550.Currently comparing calibration methods for 4-port measurements. WinCal Hybrid LRRM-SOLR - needs the switching error terms. Cascade's results suggest that the only accurate way to get these is using an ECal module. Is there any other way to determine them if we don't have ECal? PNA on-board SOLR - would seem to be the most accurate, but I've read that this also needs to know the switching error terms. Is this true? If so, how does the PNA get around the problem with not having enough receivers to determine these error terms? PNA on-board SOLT - seems to give inaccurate results above 30GHz, I suppose because of the non-ideal thru?Is it likely that a 3-port calibration will be more accurate than a 4-port one?Thanks for your help,James"
"Thanks for all the help!BTW, we don't have ECal, and we are doing on-wafer calibration. I understand now that it's probably better to run the onboard calibration routines (rather than WinCal) so that unknown thrus can be used without needing separate switching terms determination. We've got firmware A.06.03.05. I notice that when I start up the calibration, there's check box for 'select delta cal'. So, is it true that I don't need to check this box in order to do unknown thru cal, as long as I've got a known thru touching all of the ports? Or does the firmware need to be upgraded in order for the VNA to be able to calculate the switching terms from the known thrus?One other question - 4-port calibration requires only 3 thrus, but would better accuracy be achieved if a fourth thru is included as well?Thanks,James"
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