A flat antenna for satellite communication includes a radiating board. The radiating board includes at least one radiating line, and an adapter configured to modify the delay of the fields transmitted or received by the radiating line. The adapter includes a horn mobile in rotation between the two metal plates containing a sensor array. The horn is also mobile in rotation between at least one coaxial cable connected between at least one sensor of the network and the radiating line. The length of the coaxial cable is suitable for introducing a delay required to focus the wave radiated by the radiating line.