Cool VNA calibration paper: Backward-Unknown-Thru. Instead of SOLR (which is just SOLT with an unknown adapter), in the Backward-Unknown-Thru, you measure a flush Thru at the near end of the test cables, and do two 1-port calibrations at the far end. The solved Unknown Thru will have a negative length, which is the "mirror image" of the test cable error. Great if the two far-end ports are really "far". Even better, you can measure the 2-port Thru first, before doing two 1-port calibrations, this way the cable movement error is absorbed into the error box. #electronics #vna

* J.-H. Kim, J.-S. Kang, J.-I. Park, and C.-H. Cho, “Backward Unknown-Thru calibration method,” in 2020 95th ARFTG Microwave Measurement Conference (ARFTG), Aug. 2020, pp. 1–3. 10.1109/ARFTG47271.2020.9241362.