An ortho-mode transducer (100) comprising a first part (102) with a first port (106) for connecting a first rectangular waveguide (112) and a second port (108) for connecting a second rectangular waveguide (114). The signals in the two waveguides have orthogonal polarizations. The transducer also comprises a second part (104) with a third port (110) for connecting a common circular waveguide (116) in which the two orthogonal signals can be propagated. Symmetry axes of cross sections of the first and the second waveguides have orthogonal orientation. The first rectangular port (106) has its broad walls perpendicular to the circumference of the common circular waveguide (116) and the second rectangular port (108) has its broad walls alongside the circumference of the common circular waveguide. The first and second ports are connected to the third port in opposite positions via 90- degree bends (118, 120). In a coupling region a separating plate extends from a wall closing the common circular waveguide, wherein the separating plate is oriented perpendicular to the longitudinal axes of parts of the rectangular ports coupled to the common circular waveguide.