X-Ray Computed Tomography for 3D Characterization of High-Frequency Standards

This paper presents a non-contact method for the characterization of coaxial air-dielectric transmission lines used as S-parameter standards. The use of computed tomography for measuring the diameter of the outer conductor of a line is introduced. The proposed method utilizes 3D reconstruction to obtain a mean diameter by fitting small cylinders into the object. This result is necessary to calculate the characteristic impedance of the line and derive its S-parameters. The procedure is traceable to the SI base unit of length and, due to its advantages, can serve as a complement to other established methods of measurement.