An antenna comprises a substrate, a feed conductor, a ground layer, a resonator and a short-circuited element. The substrate comprises a first surface and a second surface. The feed conductor is formed on the first surface. The ground layer is formed on the second surface, comprising an aperture. The resonator is disposed on the ground layer, comprising a body and a notch, the notch is formed on a first side of the body, wherein the first side is perpendicular to the ground layer. The short-circuited element is disposed on the first side connecting the ground layer.