A waveguide orthomode transducer, comprises: a junction having a main waveguide and four auxiliary waveguides lying along the two orthogonal main axis of the junction and defining four quadrants; a combination network comprising: two magic tees, each having an E-port, two opposed common-ports, and a H-port; an H-plane tee junction having a Σ-port and two opposed common-ports; and an E-plane tee junction having a Δ-port and two opposed common-ports. Two auxiliary waveguides define a first quadrant are respectively connected to the common-ports of one of the magic tees and the two other secondary waveguides defining a second quadrant opposite to the first quadrant are connected to the common-ports of the other magic tee. The tee junctions are used to connect similar magic tee ports so that the transducer separates towards two different outputs two orthogonally polarized signals entering at the main waveguide. Reciprocally, two signals entering respectively in the Σ-port and the Δ-port of the tees junctions are combined with orthogonal polarizations in the main waveguide.