The invention relates to an antennal structure adapted to be disposed on an earth plane comprising: a three-dimensional support substrate made of a dielectric material which is partially hollowed out and comprising a peripheral wall which extends between a proximal end and a distal end, said support substrate defining an internal volume; a first conducting pattern inscribed on the peripheral wall of the support substrate, the first conducting pattern comprising a lower end adapted to be connected to an earth plane and an upper end; a second conducting pattern contained in the volume of the substrate, the second pattern being connected electrically to the upper end of the first pattern.