Dual-band electromagnetic coupler

A coupler with mode transformer, for coupling (a) a common square waveguide port supporting at least one of two mutually spatially orthogonal linear polarizations with at least one of nominally mutually independent (b) first external and (c) second external ports, said first external port being in the form of a cluster of first, second, third, and fourth clustered square waveguide ports, any one of which is capable of supporting at least one of two mutually spatially orthogonal linear polarizations, and said second external port being in the form of first and second rectangular ridged waveguide ports, each of which is capable of supporting a single linear polarization, said coupler comprising:

• a ridged square waveguide section defining a first port coupled to said common square waveguide port and also defining a second port, said ridged square waveguide section including first and second mutually spatially orthogonal ridge structures lying between said first and second ports of said ridged square waveguide section, which ridge structures tend to concentrate the fields of the dominant TE1,0 mode of either of said two mutually spatially orthogonal linear polarizations in a region near the center of said ridged square waveguide section, said ridged square waveguide section also including first and second planar phase shifters, said first planar phase shifter lying parallel to said first ridge structure, and said second planar phase shifter lying parallel with said second ridge structure, so that said first and second planar phase shifters are mutually orthogonal, each of said first and second planar phase shifters being located between that one of said ridge structures with which it is parallel and a side wall of said ridged square waveguide section, for propagating either polarization of said dominant TE1,0 mode from said first port to said second port of said ridged square waveguide section without substantially affecting said dominant TE1,0 mode, and for delaying by substantially π a spatial portion of one of (a) a TE20 and (b) a TE0,2 mode propagating therein, to thereby convert between said dominant TE1,0 mode at said first port of said square waveguide section and said one of said (a) TE20 and (b) TE0,2 mode at said second port of said square waveguide section;
• a transition section of waveguide, said transition section of waveguide defining a first square waveguide port which is coupled to said second port of said ridged square waveguide section, said transition section of waveguide including a first septum extending completely across said square cross-section at said second port of said transition section of waveguide to thereby define first and second internal rectangular waveguide ports, said first septum progressively reducing in size toward said first square waveguide port of said transition section of waveguide, said transition section of waveguide being for converting between said either polarization of said TE1,0 mode at said second port of said ridged waveguide section and the TE1,0 mode in said first and second internal rectangular ports of said transition section;
• and
• an eight-port waveguide branch section defining said first and second rectangular ridged waveguide ports of said second nominally independent port of said coupler, said first, second, third, and fourth clustered square waveguide ports of said first nominally independent port of said coupler, and third and fourth internal rectangular waveguide ports having a common wall, said third and fourth internal rectangular waveguide ports of said branch section being coupled to said first and second internal rectangular waveguide ports of said transition waveguide section, said branch section further defining first and second H-plane walls parallel with said common wall, a first E-plane rectangular aperture in said first H-plane wall which is coupled to said first rectangular waveguide port of said second nominally independent port of said coupler, and a second rectangular aperture in said second H-plane wall which is coupled to said second rectangular waveguide port of said second nominally independent port of said coupler, said branch section further including a second septum extending from that edge of said first rectangular aperture which is adjacent said first nominally independent waveguide port to said first nominally independent waveguide port, to thereby aid in defining said first and second clustered square waveguide ports, and further including a third septum extending from that edge of said second rectangular aperture which is adjacent said first nominally independent waveguide port to said first nominally independent waveguide port, to thereby aid in defining said third and fourth clustered square waveguide ports.