On-line accuracy assessment for the dual six-port ANA: Experimental results

When a calibration laboratory such as the National Bureau of Standards (NBS) performs a measurement for a customer, the accuracy the laboratory attaches to its measurements is a significant part of the customer's report. In some instances, the accuracy statement may be more important to the customer than the measurement itself. Modern automated measurement systems can often perform hundreds of measurements in a fraction of a second. However, few, if any, of these systems attempt to assess the accuracy of those measurements in a real-time or on-line basis. The accuracy of a modern automatic network analyzer (ANA) is a function of a number of variables. Connector quality, operator technique, system hardware, and system calibration are just a few of the many parameters that affect the day-to-day accuracy of an automated system. This paper describes the results of the current efforts at NBS to implement on-line accuracy estimates for its dual six-port network analyzers. Results are presented showing uncertainty estimates obtained in quasi-real time during the measurement of customers devices.