In order to have complete confidence in your S-parameter measurements , it is critical to characterize the uncertainty contribution of each aspect of your test setup.
Starting with the VNA, users can characterize the uncertainty for the specific settings used to measure their device under test, including IF bandwidth, port power and averaging. VNA uncertainty is related to the VNA noise floor including the noise floor itself, and the magnitude and phase of the trace noise.
Users can also characterize the uncertainties of VNA drift over time including switch terms, tracking magnitude and phase, symmetry magnitude and phase, match, directivity and isolation. These uncertainties are measured and quantified for the specific VNA in use and do not rely on any generalized or specific data provided by the VNA manufacturer.
VNA calibration kit uncertainties can be loaded if provided by the cal kit manufacturer. Maury’s characterized device CD cal kits, model CK50 and CK51, include uncertainty data for each calibration standard.
Measurement uncertainties caused by cable flexure can be characterized using Insight. Cable transmission uncertainty is characterized by connecting a short circuit termination to the end of the cable and performing multiple measurements while bending the cable in the same manner that a user would bend the cable during their measurements. This ensures that the uncertainty is quantified for the specific movements associated with each user’s test, and not a generalized or ideal bend. This test does not rely on any data or information provided by the cable vendor.
Likewise, cable reflection uncertainty is characterized by connecting a 50 ohm load termination to port 1 and repeating the measurement while bending process. Like the previous test, this does not rely on any data or information provided by the cable vendor.
The final connection interface at the calibrated device reference plane can be characterized for uncertainty by connecting and measuring a short circuit termination, then disconnecting and rotating the short circuit by 45 degrees and remeasuring, and repeating the process N times. This will characterize the measurement repeatability, capturing any issues caused by connector pin depth and concentricity, as well as user errors caused by poor connector etiquette.