Compact T-junction orthomode transducer facilitates easy integration and low cost production

A novel waveguide T-junction is shown to provide the basic building block of a very compact OMT design. It is formed by a short circuited common circular (or square) waveguide section exhibiting two rectangular waveguide ports at the short circuit situated at opposed side walls - one with an E- and the other with an H-plane alignment. Thus the orthogonal modes (polarizations) of the common waveguide are coupled by different field components at the side wall ports, i.e., the E-plane waveguide port couples the H_χ-fields of the 1^st polarization (TE_11s/TE₀₁) while the H-plane port serves the H_z-fields of the orthogonal one (TE_11c/TE₁₀). High isolation between the orthogonal polarized signals is obtained due to the symmetry and the port alignment of the structure. The implementation of appropriate discontinuities within the T-junction allows the realization of a single-acting OMT solution with high performance properties. The approach is verified by a realized OMT design at 26GHz that is made from a single block by CNC machining.