A dual-reflector antenna comprises a main reflector traversed by a feed source and a sub-reflector. The sub-reflector comprises a dielectric body extending between a first end that is small in diameter and a second end that is greater in diameter, the small-diameter end being connected to the end of the feed source constituted by a metal tube filled with a dielectric material. The end of the feed source connected to the sub-reflector comprises a housing, having an inner depth and inner diameter, built into the dielectric material. The small-diameter end of the sub-reflector comprises an inner portion having a substantially cylindrical shape, able to fit into the housing, having an outer length and outer diameter. The outer length and outer diameter of the small-diameter end of the sub-reflector are respectively less than the inner depth and inner diameter of the feed source, so as to form a space between the inner portion of the sub-reflector and the dielectric wall of the housing.