Surface Roughness Effects of Fabrication Technology on Metallic Waveguide in D-Band for 6G RF Communications

This paper presents on the effect of surface roughness characteristics for metallic waveguide in D-Band (110 GHz∼170 GHz) which is a candidate component technology for 6G mobile RF communications. D-band RF components based on the waveguide have been widely used in existing wireless communications system. The surface roughness characteristics of metallic waveguide in D-band should be considered due to the short wavelengths. Generally, the common technologies of fabricating waveguides in D-band include the metallic 3D printing, CNC machining, etc. Each fabrication method basically provides the specifications for metallic surface such a particle size and surface roughness. However, it is difficult to predict the performance of the metallic waveguide based on only these parameters of fabrication methods. In this paper, we calculated the attenuation factor for surface roughness using the Huray model and each fabrication technology parameter. And the line loss of the metallic waveguide in D-band for each fabrication technology was simulated by applying the calculated attenuation factor to the 3D EM simulation (Ansys HFSS). Simulated waveguide structure was WR-7 type with 1.7mm width and 0.83mm height, and a length of waveguide was 10mm (5λ
0
at 150GHz). The fabrication types of waveguide included the metallic 3D printing, conventional CNC machining, nano CNC machining, and no surface roughness case. From simulation results, it was shown that nano CNC machining technology shows the lowest loss performance, and the metallic 3D printing has the worst performance. By using the proposed prediction strategy, surface roughness loss of waveguide components in D-band can be predicted, and this low loss waveguide fabrication technology might be useful for constructing the 6G mobile RF communication test system.