Patent ID: 8854274

Claim:
An antenna device comprising: a non-conductive substrate having a short edge, and two long edges connected respectively to two opposite ends of said short edge and substantially parallel to each other; an unbalanced antenna being disposed on said non-conductive substrate proximate to said short edge of said non-conductive substrate and having a ground portion; a ground plane disposed on said non-conductive substrate, located at one side of said unbalanced antenna, and electrically coupled to said ground portion, said ground plane having two opposite side edges that extend along said two long edges of said non-conductive substrate, said ground plane having a length longer than a quarter of an equivalent wavelength corresponding to an operating frequency of said unbalanced antenna; and a pair of choke sleeve structures symmetrically disposed on said ground plane at locations which are inwardly of said two opposite side edges of said ground plane and which are spaced apart from said unbalanced antenna by about a quarter of the equivalent wavelength corresponding to the operating frequency, each of said choke sleeve structures having a first end connected to said ground plane, and a second end extending in a direction away from said unbalanced antenna.