Abstract: Embodiments of the present invention concerns an aperture antenna that comprises: a receiving element, which includes an aperture and is configured to receive, through the aperture, radio signals having frequencies within a given band of radio frequencies; a waveguide configured to receive radio signals from the receiving element; and a frequency selective structure, which is arranged between the receiving element and the waveguide, and comprises metamaterial structures that extend partially inside the receiving element and/or partially inside the waveguide and that are configured to cause the propagation, from the receiving element to the waveguide, of only the received radio signals that have frequencies comprised within a predetermined sub-band of the given band of radio frequencies. Furthermore, the frequency selective structure is configured to reflect back into the receiving element the received radio signals that have frequencies not comprised in the predetermined sub-band.