Antenna assembly, comprising: - a single substrate having a lower surface and an upper surface; - a ground plane formed on the lower surface of the substrate constituted by a metallic deposit on the entire lower surface; - an antenna element formed on the upper surface of the substrate said antenna element being constituted by a periodic patterns metasurface formed on the substrate by a texture of subwavelength patches, said antenna element being constituted of - a first-scale metasurface defined by a two-dimensional alternation of metal patches (21, 22, 23) having closely spaced vertices in each contiguous element thus forming small gaps, the first-scale metasurface being defined by a two-dimensional alternation of the metal patches (21, 22, 23) and apertures (24, 25, 26); - a plurality of switches (211, 212) disposed in the gap between the vertexes of the patches, each switch (211, 212) permitting to connect several patches through the vertexes for defining a second-scale metasurface having a pattern thus forming the antenna element; wherein each patch has dimensions which do not depend on the frequency of the waves to be radiated, characterized in that the antenna assembly further comprises an isotropic source of spherical electromagnetic waves configured for emitting surface waves on the upper surface of the substrate, the antenna element being configured for transforming the emitted surface waves into leaky waves, wherein the isotropic source of spherical electromagnetic waves comprises a resonant circular patch placed at the center of the metasurface of the antenna element, wherein the patches have dimensions smaller than λ/40 where λ is the wavelength corresponding to the frequency of the waves to be radiated, wherein the resonant circular patch is printed at the same level of the metasurface of the antenna element. - a single substrate having a lower surface and an upper surface; - a ground plane formed on the lower surface of the substrate constituted by a metallic deposit on the entire lower surface; - an antenna element formed on the upper surface of the substrate said antenna element being constituted by a periodic patterns metasurface formed on the substrate by a texture of subwavelength patches, said antenna element being constituted of - a first-scale metasurface defined by a two-dimensional alternation of metal patches (21, 22, 23) having closely spaced vertices in each contiguous element thus forming small gaps, the first-scale metasurface being defined by a two-dimensional alternation of the metal patches (21, 22, 23) and apertures (24, 25, 26); - a plurality of switches (211, 212) disposed in the gap between the vertexes of the patches, each switch (211, 212) permitting to connect several patches through the vertexes for defining a second-scale metasurface having a pattern thus forming the antenna element; wherein each patch has dimensions which do not depend on the frequency of the waves to be radiated, - a first-scale metasurface defined by a two-dimensional alternation of metal patches (21, 22, 23) having closely spaced vertices in each contiguous element thus forming small gaps, the first-scale metasurface being defined by a two-dimensional alternation of the metal patches (21, 22, 23) and apertures (24, 25, 26); - a plurality of switches (211, 212) disposed in the gap between the vertexes of the patches, each switch (211, 212) permitting to connect several patches through the vertexes for defining a second-scale metasurface having a pattern thus forming the antenna element; wherein each patch has dimensions which do not depend on the frequency of the waves to be radiated, characterized in that the antenna assembly further comprises an isotropic source of spherical electromagnetic waves configured for emitting surface waves on the upper surface of the substrate, the antenna element being configured for transforming the emitted surface waves into leaky waves, wherein the isotropic source of spherical electromagnetic waves comprises a resonant circular patch placed at the center of the metasurface of the antenna element, wherein the patches have dimensions smaller than λ/40 where λ is the wavelength corresponding to the frequency of the waves to be radiated, wherein the resonant circular patch is printed at the same level of the metasurface of the antenna element.