A ring-centered waveguide flange for millimeter- and submillimeter-wave applications

Waveguide flanges pose a major limitation to precise measurements above 110 GHz. This paper describes measurements on a new flange which is compatible with the standard UG-387 waveguide interface (MIL-DTL-3922/67C) but which offers significant improvement in alignment and repeatability. The ring-centered flange has a precisely machined boss centered on the waveguide aperture. The bosses of a mated pair of flanges are aligned by a separate coupling ring. The new flange is sexless and the contact surfaces are accessible for mechanical lapping to repair damage. Measurements of WR-5 waveguides (140-220 GHz) with ring-centered flanges, enhanced UG-387-type flanges, and a new flange proposed by Lau and Denning are compared.