Evaluating the Uncertainty of Self-Calibrating VNA Procedures

Some important vector network analyzer (VNA) calibration procedures, such as thru-reflect-line (TRL), are not amenable to uncertainty analysis by conventional methods, because the calibration equations do not refer to the standards used. Nevertheless, by relating small changes in standard S-parameter values to corresponding changes in VNA response, sensitivity coefficients for the error coefficients obtained by calibration can be evaluated indirectly. The approach is easily implemented with uncertain-number software.