Microfabrication of a dual-mode rectangular waveguide filter

This paper reports the design and microfabrication of an F-band rectangular waveguide filter. The filter was designed to have a double-cavity structure to achieve dual-mode filtering. The filter was modeled and simulated using the commercial software, HFSS. The waveguide filter was designed to have a central frequency of 100 GHz. The prototypes of the filter were fabricated using a technology based on ultra-violet lithography of thick resist of SU-8. The fabrication errors were found to be < 5 mu m in height and 1.3A degrees in vertical angle deviations. The experimental results of the filters were found to be in agreement with those from numerical simulations, with the insert loss at 0.8 dB and the return loss better than 15 dB. The study has confirmed the feasibility of the filter and the fabrication technology. Because the structural material of this waveguide filter is polymer, batch fabrication with low cost replication using PDMS intermediate mold can be readily adopted as commonly practiced in the field of polymer-based microfabrication. This technology therefore may potentially reduce the production cost of millimeter wave filter dramatically.