Abstract: The invention relates to a planar antenna 1 having surface resonators 5, which are connected via a supply network 6 to a supply point 7, the supply point 7 of the planar antenna 1 being connected via a coupling element 13 to an electronic circuit 12, particularly a converter, the coupling element 13 being a coaxial conductor in which the ratio, between the outer diameter of the inner conductor and the inner diameter of the outer conductor 17, changes between the supply point 7 of the supply network 6 and the terminal 11 of the electronic circuit 12.