Could you brief me about Feed Horn ?

Dereje,

Simply put a horn is a type of microwave antenna that somewhat resembles a horn. Typically a satellite earth station or spacecraft antenna consists of a parabolic reflector that focuses incident radio frequency (RF)  energy that it collects to a focal point in front of the antenna. The feed horn antenna is positioned so that it is in this focal point. On receive it collects the reflected and focused RF energy and transfers this signal to either a Low Noise Amplifier or a Low Noise Block down converter depending on the receive system architecture design. On transmit the amplified carrier is sent or fed to the feed horn antenna. The feed horn is aimed at the reflector. The energy from the feed horn is reflected and focused into a beam by the reflector.