Ortho-mode transducer with wide bandwidth branch port

An ortho-mode transducer comprising:

• a cylindrical common waveguide terminating in a common port;
• a generally rectangular vertical branch waveguide in-line with the cylindrical common waveguide, the vertical branch waveguide terminating in a vertical port opposed to the common port, the vertical branch waveguide configured to couple a first linearly polarized mode from the vertical port to the common waveguide, a portion of the vertical branch waveguide overlapping a portion of the cylindrical common waveguide;
• a septum spanning a long dimension of the vertical branch waveguide proximate to the overlapping portions of the vertical branch waveguide and the common waveguide;
• a generally rectangular horizontal branch waveguide normal to the common waveguide and the vertical branch waveguide, the horizontal branch waveguide terminating in a horizontal port, the horizontal branch waveguide configured to couple a second linearly polarized mode from the horizontal port to the common waveguide, the second linearly polarized mode orthogonal to the first linearly polarized mode;
• and
• a generally rectangular symmetry cavity opposed to the horizontal branch waveguide.