A log-periodic antenna, which comprises at least one set of three radiating elements with log-periodic patterns (E 1, E 2, E 3) and a flat substrate which defines an electrical ground of the antenna, the radiating elements with log-periodic patterns being positioned above a first face of the flat substrate, each radiating element with log-periodic patterns comprising a succession of radiating dipoles distributed on either side of a rectilinear electrically-conductive line (R 1, R 2, R 3), perpendicularly to said line, the radiating dipoles having a dimension increasing between a first end of said line and a second end of said line located closer to said first face than the first end, a first radiating element (E 2) having a rectilinear electrically-conductive line substantially perpendicular to said first face, a second radiating element (E 1) and a third radiating element (E 3) being located on either side of the first radiating element (E 2), symmetrically to the first radiating element (E 2), the first ends of the electrically-conductive lines of the different radiating elements being spaced away from each other and substantially aligned according to a direction parallel to the first face, the rectilinear electrically-conductive line of the second and third radiating elements being located in a same plane as the rectilinear electrically-conductive line of the first radiating element and the radiating dipoles of the three radiating elements being either substantially perpendicular to the plane that contains the rectilinear electrically-conductive lines of the three radiating elements, or substantially in the plane that contains the rectilinear electrically-conductive line of the three radiating elements, characterised in that each first end being electrically connected to a different coaxial cable, the rectilinear electrically-conductive lines of the second and third radiating elements being inclined with respect to the electrically-conductive line of the first radiating element such that the first ends of the rectilinear electrically-conductive lines of the second and third radiating elements are closer than the second ends of the rectilinear electrically-conductive lines of said second and third radiating elements, wherein: - the distance that separates the radiating dipole with the smallest dimensions of the second radiating element (E 2) from the radiating dipole with the smallest dimensions of the first radiating element (E 1) and the distance that separates the radiating dipole with the smallest dimensions of the third radiating element (E 3) from the radiating dipole with the smallest dimensions of the first radiating element (E 1) are substantially comprised between 0.6λ HF and 0.7λ HF, where λ HF is a wavelength of a high-frequency wave radiated by the log-periodic antenna, and - the distance that separates the radiating dipole with the largest dimensions of the second radiating element (E 2) from the radiating dipole with the largest dimensions of the first radiating element (E 1) and the distance that separates the radiating dipole with the largest dimensions of the third radiating element (E 3) from the radiating dipole with the largest dimensions of the first radiating element (E 1) are substantially comprised between 0.6λ BF and 0.7λ BF, where λ BF is a wavelength of a low-frequency wave radiated by the log-periodic antenna. - the distance that separates the radiating dipole with the smallest dimensions of the second radiating element (E 2) from the radiating dipole with the smallest dimensions of the first radiating element (E 1) and the distance that separates the radiating dipole with the smallest dimensions of the third radiating element (E 3) from the radiating dipole with the smallest dimensions of the first radiating element (E 1) are substantially comprised between 0.6λ HF and 0.7λ HF, where λ HF is a wavelength of a high-frequency wave radiated by the log-periodic antenna, and - the distance that separates the radiating dipole with the largest dimensions of the second radiating element (E 2) from the radiating dipole with the largest dimensions of the first radiating element (E 1) and the distance that separates the radiating dipole with the largest dimensions of the third radiating element (E 3) from the radiating dipole with the largest dimensions of the first radiating element (E 1) are substantially comprised between 0.6λ BF and 0.7λ BF, where λ BF is a wavelength of a low-frequency wave radiated by the log-periodic antenna.