Uncertainty of VNA S-parameter measurement due to non-ideal TMSO or LMSO calibration standards

摘要

For the widespread 12-term TMSO and LMSOcalibration of 4-sampler vector network analyzers (VNA),the sensitivity coefficients of the S-parameters of two-portsare developed as functions of the deviations of the reflectioncoefficients of the one-port calibration standards and ofan imperfect through or line connection. Expressions representingthe deviations of the S-parameters with respectto the error terms and for the deviations of the error termswith respect to the non-ideal calibration standards are alsogiven. It is shown that the deviations of the S-parametersbecome quite large particularly for high-reflective two-porttest objects. If applying a broadband load (instead of usingthe time consuming “ideal" sliding load routine) and theVNA-internal firmware-operated calibration and evaluationroutines where the reflection coefficient is set to zero, deviationsmay appear of some 0,1 dB for the attenuation andsome degrees of the transmission phase angle.