Advances in Radio Science www.adv-radio-sci.net 1684-9965 1684-9973 1 Kleinheubacher Berichte 2002 2003 10.5194/ars-1-1-2003 http://www.adv-radio-sci.net/1/1/2003/ http://www.adv-radio-sci.net/1/1/2003/ars-1-1-2003.html http://www.adv-radio-sci.net/1/1/2003/ars-1-1-2003.pdf 1 8 2003-05-05 Uncertainty of VNA S-parameter measurement due to non-ideal TMSO or LMSO calibration standards U. Stumper Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany For the widespread 12-term TMSO and LMSO calibration of 4-sampler vector network analyzers (VNA), the sensitivity coefficients of the S-parameters of two-ports are developed as functions of the deviations of the reflection coefficients of the one-port calibration standards and of an imperfect through or line connection. Expressions representing the deviations of the S-parameters with respect to the error terms and for the deviations of the error terms with respect to the non-ideal calibration standards are also given. It is shown that the deviations of the S-parameters become quite large particularly for high-reflective two-port test objects. If applying a broadband load (instead of using the time consuming “ideal" sliding load routine) and the VNA-internal firmware-operated calibration and evaluation routines where the reflection coefficient is set to zero, deviations may appear of some 0,1 dB for the attenuation and some degrees of the transmission phase angle.