Patent ID: 6570538
Filing Date: 2003-05-27
Classification: H01Q

Abstract:
An antenna structure, comprising at least one active and at least one parasitic antenna conductor and arranged to be fitted on top of a planar electroconductive surface at a distance from said surface which is arranged to operate 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 Â¼ of the wavelength of the used frequency and which are substantially parallel with said ground plane, and which comprise opposite first ends and opposite free second ends, wherein the antenna structure is further equipped with symmetrical conductors at the first ends for short-circuiting the first ends to said ground plane and a first conductor for coupling a supply of radio frequency energy to a desired point between a first end and a second end of the active antenna conductor, wherein the antenna structure also includes a second conductor symmetrical to the first conductor for coupling a short circuit to the ground plane at a corresponding point between a first end and a second end of the parasitic antenna conductor in such a way that when the antenna structure is rotated 180Â°, the second conductor is, in turn, used as said supply and the first conductor is, in turn, used as said short circuit.