Four port frequency diplexer

Abstract From the Canadian patent

A diplexer for communicating signals in two different frequency bands with separate polarizations in each band may, for example, concurrently separate low frequency received signals of orthogonal polarizations from high frequency transmitted signals also of, orthogonal polarizations. To this end a common square waveguide leads to serially disposed, axially displaced orthogonal mode transitions at which branches are made to closely coupled lowpass filters that communicate with separate ports for low frequency signal bands. A smaller square waveguide coupled to the second of the orthogonal mode transitions communicates with another orthogonal mode transition at which axially displaced …