Experimental Determination of the Internal Aperture Dimensions of Sub-Terahertz Waveguides

Waveguide lines form fundamental building blocks of high frequency transmission systems. For waveguides operating at sub-terahertz (THz) frequencies, i.e. from 300 GHz to 1 THz, the challenges in characterizing such lines increase significantly due to factors such as their small physical dimensions. This paper reports on the use of the primary measurement system for the WM-380 band (500 to $\mathbf{7 5 0} \mathbf{G H z}$) at the UK’s National Physical Laboratory (NPL) for electrically measuring lines in this sub-THz band. The measurement results are used in conjunction with conventional models for transmission lines in order to determine values for the aperture dimensions of the lines, which would otherwise be extremely challenging to obtain due to the small physical dimensions involved.