An active antenna is disclosed including a passive portion of an antenna array extended at one end by a plate in which apertures are formed, at least one active assembly for transmitting radiofrequency RF waves, called assembly, through said apertures, each assembly including a first row of active modules facing apertures of the plate, a second row of active modules facing apertures of the plate and attached to the first row of active modules, a beam attached to the plate and held clamped between the first and second rows of active modules, a heat-transfer duct in contact with the first and second rows of active modules and jutting out on either side of said first and second rows of active modules.