An antenna formed by a hole in a conducting plane that is excited by a feed connected at points around the edge. The points may be fed via a conducting tube as in a horn antenna. Aperture antennas have an advantage over other antennas in that they may have a very low profile. They are thus very useful in aerospace applications where they can be mounted flush with the skin of an aircraft. In these cases they can easily be covered with a dielectric material for protection.