Symmetrical antenna structure and a method for its manufacture as well as an expansion card applying the antenna structure

Abstract

An antenna structure which comprises at least one active and at least one parasitic antenna conductor and which is arranged to be fitted on top of a planar electroconductive surface at a distance from said surface which is arranged to be used as a ground plane for said antenna structure, and which antenna structure comprises, arranged parallelly at a distance from each other, a first antenna conductor and a second antenna conductor which have an electrical length of approximately ¼ of the wavelength of the used frequency and which are parallel with said ground plane, and which comprise opposite first ends and opposite free second ends, wherein the antenna structure is equipped with symmetrical conductors for short-circuiting the first ends to said ground plane and a first conductor for coupling the supply to a desired point between the first end and a second end of the active antenna conductor. The antenna structure is symmetrically equipped with also a second conductor for coupling a short circuit to the corresponding point between the first end and the second end of the parasitic antenna conductor in such a way that in the rotated position of 180° of the antenna structure, the second conductor is, in turn, used as said supply and the first conductor is, in turn, used as said short circuit.