A antenna made from a photonic band-gap (PBG) material, includes: a lateral wall (4) which is made from a PBG material and which completely surrounds a central axis (6), the wall being disposed at a distance from the central axis such as to form a central resonant cavity; and at least one radiating element (34) which is placed inside the cavity. Each radiating element is positioned inside the cavity in order to excite an electromagnetic field parallel to the central axis and the radiating element(s) can excite the modes of the central cavity having a radial resonance more strongly than the other modes of the cavity.