A cladding (2) for a microwave antenna comprises at least one plate (3a, 3b, 3c, 3d) which has, in a first section plane (x=0; y=0), a cross section in the shape of a logarithmic spiral, characterized in that the plate (3a, 3b, 3c, 3d) has a cross section in the shape of a logarithmic spiral also in at least one second section plane perpendicular to the first one.