A feed for a dual-band antenna, comprising - a waveguide structure comprising: ∘ a first waveguide configured to communicate first electromagnetic radiations falling in a first frequency range, wherein the first waveguide extends along a longitudinal direction, and ∘ a second dielectric waveguide located within said first waveguide, said second waveguide being configured to communicate second electromagnetic radiations, said second electromagnetic radiations falling in a second frequency range, wherein the second frequency range is higher than the first frequency range, said waveguide structure having ∘ a first end whose extremity is configured to pass both first and second electromagnetic radiations, ∘ a second end connected to: ▪ a low band port configured to pass said first electromagnetic radiations, and ▪ a high band port configured to pass said second electromagnetic radiations, wherein the first waveguide comprises: ∘ a first section extending from said first end along said longitudinal direction, and ∘ a second section extending along said longitudinal direction until said second end, wherein a minimal distance between an internal surface of walls of the first section of said first waveguide and an external surface of walls of the second dielectric waveguide is D 11 along a lateral direction orthogonal to said longitudinal direction, and wherein a maximal distance between an internal surface of at least one first wall of the second section of the first waveguide and an external surface of a wall of the second dielectric waveguide facing said first wall is D 12 along said lateral direction, wherein D 12 <D 11,wherein the waveguide structure further comprises a protrusion located at said second end, characterized in that the protrusion comprises a portion extending from said at least one first wall towards the low band port along a distance D 2, wherein D 2 is less or equal to λ 1, wherein λ 1 is a central wavelength of the first electromagnetic radiations. - a waveguide structure comprising: ∘ a first waveguide configured to communicate first electromagnetic radiations falling in a first frequency range, wherein the first waveguide extends along a longitudinal direction, and ∘ a second dielectric waveguide located within said first waveguide, said second waveguide being configured to communicate second electromagnetic radiations, said second electromagnetic radiations falling in a second frequency range, wherein the second frequency range is higher than the first frequency range, said waveguide structure having ∘ a first end whose extremity is configured to pass both first and second electromagnetic radiations, ∘ a second end connected to: ▪ a low band port configured to pass said first electromagnetic radiations, and ▪ a high band port configured to pass said second electromagnetic radiations, ∘ a first waveguide configured to communicate first electromagnetic radiations falling in a first frequency range, wherein the first waveguide extends along a longitudinal direction, and ∘ a second dielectric waveguide located within said first waveguide, said second waveguide being configured to communicate second electromagnetic radiations, said second electromagnetic radiations falling in a second frequency range, wherein the second frequency range is higher than the first frequency range, said waveguide structure having ∘ a first end whose extremity is configured to pass both first and second electromagnetic radiations, ∘ a second end connected to: ▪ a low band port configured to pass said first electromagnetic radiations, and ▪ a high band port configured to pass said second electromagnetic radiations, ▪ a low band port configured to pass said first electromagnetic radiations, and ▪ a high band port configured to pass said second electromagnetic radiations, ∘ a first section extending from said first end along said longitudinal direction, and ∘ a second section extending along said longitudinal direction until said second end, wherein a minimal distance between an internal surface of walls of the first section of said first waveguide and an external surface of walls of the second dielectric waveguide is D 11 along a lateral direction orthogonal to said longitudinal direction, and wherein a maximal distance between an internal surface of at least one first wall of the second section of the first waveguide and an external surface of a wall of the second dielectric waveguide facing said first wall is D 12 along said lateral direction, wherein D 12 <D 11,wherein the waveguide structure further comprises a protrusion located at said second end, wherein a minimal distance between an internal surface of walls of the first section of said first waveguide and an external surface of walls of the second dielectric waveguide is D 11 along a lateral direction orthogonal to said longitudinal direction, and wherein a maximal distance between an internal surface of at least one first wall of the second section of the first waveguide and an external surface of a wall of the second dielectric waveguide facing said first wall is D 12 along said lateral direction, wherein D 12 <D 11,wherein the waveguide structure further comprises a protrusion located at said second end,