Using electromagnetic modeling to evaluate uncertainty in a millimeter-wave cross-guide verification standard

This paper describes some investigations, made using electromagnetic modeling, into the uncertainty for a cross-guide verification standard of transmission loss for waveguide Vector Network Analyzers (VNAs) operating at millimeter-wave frequencies. The cross-guide is calculable and can be made traceable to the International System of units (SI) via precision dimensional measurements of the waveguide aperture and flange. The measurement errors due to dimensional tolerances of the cross-guide line (including waveguide aperture height, width, corner radii and waveguide line length) and the mechanical discontinuity between the cross-guide and the VNA test ports (including the connection angle) can be predicted from electromagnetic theory. The measurement uncertainty due to these errors can be calculated according to the Law of Propagation of Uncertainty. The paper describes these details, and compares experimental results, obtained using a VNA operating in the 140 GHz to 220 GHz band, with simulated values evaluated by electromagnetic modeling software.