Trends of Traceability and Accuracy Assessment in Vector Network Analyzer

Modern Vector Network Analyzers are powerful vector measurement systems for high frequency device characterization, in terms of scattering parameters. These instruments need a complex calibration procedure, aimed to remove the greater part of the errors associated to the hardware and to trace measurements to primary standards. Actually, these primary standards are only indirectly associated to SI fundamental electrical quantities. The more suitable standards are sections of transmission lines, characterized by means of dimensional measurements. The system accuracy is mainly related to the uncertainty of the standards , which propagates to the calibration coefficients of the network analyzer, according to the algorithms used by the calibration process. Systematic errors not removed by the calibration process, define a scattering matrix that must be anyway evaluated, for the final measurement uncertainty. Network Analyzer accuracy assessment after calibration process is widely described in the literature, but some clarifications are necessary, in order to avoid not consistent interpretations. For the same reasons, the measurand analysis would need a revision. Indeed, also in high-level comparisons, discrepancies arise among participants using instrumentation of equivalent performances, a result clearly due to different interpretation of the analysis rules. The authors suggest simple principles, in order to improve the harmonization of the measurement results.