Abstract: The invention relates to an antenna source transmitting and receiving polarized microwaves, the source including a transducer for separating the transmission signals from the reception signals, the frequencies of the transmission signals being different from the frequencies of the reception signals. The connection between the transducer and the radiating element of the antenna is such that it maintains the polarization states of the signal received by the radiating element and of the signal transmitted to said radiating element. The transducer comprises a square-section waveguide, one end of which is connected to the radiating element, the other end being connected to the transmission path, the received signals being conveyed by the side faces of the waveguide. This source makes it possible to transmit and to receive in the enlarged C band, i.e. 3.4 GHz to 4.2 GHz on reception, and 5.85 GHz to 6.65 GHz on transmission.