The invention relates to an antenna comprising a resonant cavity deliminated by a partially reflecting surface comprising an array of resonant cells, each resonant cell forming a micro-antenna, a totally reflecting surface facing said partially reflecting surface, a radiating source disposed in said resonant cavity and configured so as to radiate a wave between the partially reflecting surface and the totally reflecting surface, said wave illuminating resonant cells of the partially reflecting surface, the partially reflecting surface being curved and resonant cells being individually configured to introduced upon the passage of the incident wave radiated by the source a phase shift dependent on the curvature of the partially reflecting surface at the level of the corresponding resonant cell.