A lens antenna of Luneberg type comprising a disc-shaped dielectric element having a radially varying diffraction index and bounded on both major sides by conductive metal plates. The antenna is preferably adapted for transmission of a wave which is polarized in an angle of 45.degree. relative to the plane of the lens element and is characterized in that the distance between the conductive plates and the lens element is filled with air or a dielectric having a corresponding dielectric constant.