The present invention relates to an active device comprising an active element composed of a cylindrical dipole structure divided into a positive region and a negative region spaced apart from the positive region and an active element disposed on at least one side of the active element, There is provided a dipole ESPAR antenna including a positive pattern and a parasitic element spaced apart from the positive pattern and formed of a planar dipole structure divided into a negative pattern electrically connected to the negative region .
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