Metal Sheet Thickness Measurement using Dielectric Waveguides with Millimeter Wave Radar

In this paper, we present thickness measurements of metal sheets with a single millimeter wave radar. Dielectric waveguides (DWGs) are used to split and guide electromagnetic waves to focusing lens antennas on both sides of the sheet. Both, the DWG and the lens antennas are 3D printed. To cover larger dimensions than the printing area of the 3D printer, a concept to connect DWGs is presented. Furthermore, the transition from the DWG into the lens antenna is improved by using a pyramidal horn with a square cross-section. The presented measurement setup allows simple reference measurements to compensate for systematic errors, leading to a maximum absolute error of 4 μm. A standard deviation of 1 μm for individual sheets confirms the proposed measurement principle.