Traceability via precision dimensional measurements of WM-864 (WR-03) waveguide standard shims including comparison between NPL and NMIJ

This paper presents a measurement comparison of WM-864 (WR-03) precision waveguide lines for use as reference standards in the Thru-Reflect-Line (TRL) calibration method for VNAs at millimeter and sub-millimeter wave frequencies (in this case, from 220 GHz to 330 GHz). The measurement is established using three-dimensional Coordinate Measuring Machines (CMMs) fitted with styluses that contain small-sized tips. The paper includes a comparison of these dimensional measurements, made independently at the national metrology institutes (NMIs) of Japan and the United Kingdom. Characteristics (e.g. reflection characteristics and scattering parameters at the waveguide interface) of these waveguide lines in the frequency-domain are also calculated and compared between these two NMIs.