A circularly polarized radiating element comprising: - at least one excitation aperture for a wave that is linearly polarized according to a first so-called excitation polarization (Ex); - a frequency selective surface that partially reflects the excitation polarization (Ex) and that is transparent to a second polarization (Ey), referred to as the orthogonal polarization, that is orthogonal to the excitation polarization (Ex) and to the direction of propagation of the wave, and that is placed in a plane defined by the excitation polarization (Ex) and by the orthogonal polarization (Ey); and further comprising a completely reflective metasurface facing the frequency selective surface, and comprising a two-dimensional and periodic array of conductive planar elements forming metasurface cells, the excitation aperture leading onto the metasurface, the frequency selective surface and the metasurface forming a resonant cavity for the excitation polarization (Ex), the metasurface cells all being oriented identically with respect to the excitation polarization (Ex) and configured to: o reflect an incident wave (Eix) according to the excitation polarization (Ex) to form a reflected wave (Er1x) polarized according to the excitation polarization (Ex), and o depolarize and reflect the incident wave (Eix) to form a reflected wave (Erly) polarized according to the orthogonal polarization (Ey), having a phase difference substantially equal to ± 90° with respect to the reflected wave (Er1x) polarized according to the excitation polarization (Ex), and having an amplitude substantially equal to the amplitude of a wave (E'tx) radiated by the frequency selective surface, generated from the reflected wave (Er1x) polarized according to the excitation polarization (Ex). - at least one excitation aperture for a wave that is linearly polarized according to a first so-called excitation polarization (Ex); - a frequency selective surface that partially reflects the excitation polarization (Ex) and that is transparent to a second polarization (Ey), referred to as the orthogonal polarization, that is orthogonal to the excitation polarization (Ex) and to the direction of propagation of the wave, and that is placed in a plane defined by the excitation polarization (Ex) and by the orthogonal polarization (Ey); and further comprising a completely reflective metasurface facing the frequency selective surface, and comprising a two-dimensional and periodic array of conductive planar elements forming metasurface cells, the excitation aperture leading onto the metasurface, the frequency selective surface and the metasurface forming a resonant cavity for the excitation polarization (Ex), the metasurface cells all being oriented identically with respect to the excitation polarization (Ex) and configured to: o reflect an incident wave (Eix) according to the excitation polarization (Ex) to form a reflected wave (Er1x) polarized according to the excitation polarization (Ex), and o depolarize and reflect the incident wave (Eix) to form a reflected wave (Erly) polarized according to the orthogonal polarization (Ey), having a phase difference substantially equal to ± 90° with respect to the reflected wave (Er1x) polarized according to the excitation polarization (Ex), and having an amplitude substantially equal to the amplitude of a wave (E'tx) radiated by the frequency selective surface, generated from the reflected wave (Er1x) polarized according to the excitation polarization (Ex). o reflect an incident wave (Eix) according to the excitation polarization (Ex) to form a reflected wave (Er1x) polarized according to the excitation polarization (Ex), and o depolarize and reflect the incident wave (Eix) to form a reflected wave (Erly) polarized according to the orthogonal polarization (Ey), having a phase difference substantially equal to ± 90° with respect to the reflected wave (Er1x) polarized according to the excitation polarization (Ex), and having an amplitude substantially equal to the amplitude of a wave (E'tx) radiated by the frequency selective surface, generated from the reflected wave (Er1x) polarized according to the excitation polarization (Ex).