In the field of circular-polarized planar wire antennas for very wide band telecommunications systems, and an antenna reflector for such an antenna, an antenna device comprises an antenna reflector and an antenna, and a method for implementing the antenna reflector. The antenna reflector comprises, on the one hand, a first reflection region exhibiting electromagnetic properties of an electrical conductor in a first sub-band of frequencies and, on the other hand, a second reflection region exhibiting electromagnetic properties akin to a magnetic conductor in a second sub-band of frequencies. Each reflection region is designed to face a region of the antenna able to emit electromagnetic radiation in the corresponding sub-band of frequencies in order to reflect the electric field of the backward radiation in phase with the electric field of the forward radiation.