Flange

Waveguide Flange

The MIL-DTL-3922/67D (often called UG-387) standard was defined in the 1960’s to ensure radar interoperability through 110 GHz (WR-10).  Beginning in 2008, the Microwave Theory and Techniques Society (MTT-S) of the IEEE has been defining a new rectangular waveguide interface standard in the P1785 Working Group for beyond 110 GHz.

http://grouper.ieee.org/groups/1785Flange_Side-by-Side_Comparison4_dv

There is a potential for misalignment in terms of four main mechanisms:  broad wall offset, narrow wall offset, rotational and diagonal.  The most significant electrical degradation occurs with broad wall and narrow wall offsets.  Furthermore, the electrical degradation in the interface quality is proportional to offset:  larger offsets cause more degradation.

An innovative and patented solution will soon become available from OML (reference US Patent 7791438).  In this approach, alignment is improved by using a concentric mating mechanism consisting of a boss and jack interface.   This novel design simplifies the tolerance build-up to just two interfaces by eliminating the need for alignment pins.  The boss & jack technology is 100% compatible with the MIL-DTL-3922/67D standard.  Contact OML for availability.

The following link overviews the popular rectangular waveguide bands and their respective cut-off frequencies and aperture dimensions.  The table also contains a close-up aperture view for relative comparison purposes.  As a rule of thumb, an engineer can quickly identify the WR number with a quick caliper measurement of the broad wall in mils (thousandths of an inch), divided by 10.  For example, a broad wall measurement of 100 mils corresponds to WR-10.

Waveguide Flange Reference Table

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